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- D A 2 7 7 2 . ., ~~ -1, 3 e, '.'e -:- -ý ~''~ r.. earco,, e.,sx~ng aata sousrces.AD -A271 372 jti, q ard oer '2, 3t
iiiiiiiii~ii~iiiii~2. REPOR T )t '-.,'JD~N DATES COVERED
4".jJJ'W0P,/LA**MENT OF INTERI1 RESPONSE ACTIONS FOR OTHER CONTAMINATION FUNDING NUMBERS
SOURCES, N-1 SI.TTLING BASINS, ROCKY MOUNTAIN ARSENAL VERSION 3.1. FINAL
6. AUTHOR(S) DAAA15 88 D 0022
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFCRMING ORGANIZATION
WOODWARD-CLYDE CONSULTANTS REPOT JUMBER
90002R05
9. SPONSORING MONITORING AGENCY NAMENS) A 10. SPONSORING! MONITORING
U I C AGENCY REPORT NUMBER
ROCKY MOUNTAIN ARSENAL (CO.). PMRMA • -', 9.. L" - E
11. SUPPLEMENTARY NOTES
12a. DISTRIBUTION i AVAILABILITY STATEMENT 12b. DIST1I13TION CODE
APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED
13. ABIT D'M0 IBES THE PROCESS AND RESULTS OF THE ALTERNATIVES
ASSESSMENT CONDUCTED FOR THE M-1 SETTLING BASINS. THESE THREE BASINS ARELOCATED IN THE SOUTH PLANTS AREA AND ARE A DIRECT SOURCE OF AS CONTAMINATION TOTHE GROUND WATER. THE GOAL OF THIS ASSESSMENT IS TO EVALUATE ALTERNATIVES BASEDUPON SUCH FACTORS AS 1) THE PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT, 2)MITIGATION OF THE THREAT TO HUMAN HEALTH, AND 3) COST.
THE ASSESSMENT IS DIVIDED INTO THE FOLLOWING SECTIONS:1. INTRODUCTION2. SITE BACKGROUND AND THE RESULTS OF CURRENT AND PREVIOUS INVESTIGATIONS3. IDENTIFICATION AND EVALUATION OF INTERIM ACTION TECHNOLOGIES4. DEVELOPMENT AND EVALUATION OF ALTERNATIVES5. COST ESTIMATES6. CONCLUSIONS.
THE PREFERRED TECHNOLOGIES ARE 1) IN-SITU VITRIFICATION AND 2) CHEMICAL
14. EC GROUNDWATER 15. NUMBER OF PAGES
"16. PRICE CODE
17. iECURITY CLASSiFICATION 18. SECURITY CLASSIFICAT;CN ' 3. SECV ITY CLASSiF!CAiIH N 20. -IMITATION OF ABSTRACTUN& fIED OF THIS PAGE •,"AGT
9 0 002R052ND COpy
FINAL ALTERNATIVES ASSESSMENTOF
INTERIM RESPONSE ACTIONSFOR OTHER CONTAMINATION SOURCES
M-1 SETTLING BASINSROCKY MOUNTAIN ARSENAL
NOVEMBER 1989CONTRACT NO. DAAA15-88-D-0022/0002
VERSION 3.1
Prepared by-
WOODWARD-CLYDE CONSULTANTS
Prepared for:
U.S. ARMY PROGRAM MANAGER'S OFFICE
FOR ROCKY MOUNTAIN ARSENAL CONTAMINATION CLEANUP
Rocky Miountai- Arsenal93-24965 ln" i"-%; itear
1IIll/llllh!!IlIJ~iIIli~ff Commerce City, Colorado
THE USE OF TRADE NAMES IN THIS REPORT DOES NOT CONSTITUTE AN OFFICIALENDORSEMENT OR APPROVAL OF THE USE OF SUCH COMMERCIAL PRODUCTS. THE REPORTMAY NOT BE CITED FOR PURPOSES OF ADVERTISEMENT.
SWoodward.Clyd C ants
3 TABLE OF CONTENTS
L0 INTRODUCTION 1-I
1.1 PURPOSE OF THE INTERIM RESPONSE ACTION (IRA) 1-1ALTERNATIVE ASSESSMENT DOCUMENT
1.2 IRA CANDIDATE SELECTION CRITERIA 1-1
13 REPORT ORGANIZATION 1-3
2.0 SITE BACKGROUND AND INTERIM ACTION INVESTIGATION 2-1
2.1 SITE DESCRIPTION 2-1
2.1.1 Location 2-12.1.2 History 2-12.1.3 Geology 2-22.1.4 Hydrology 2-5
2.1.5 Previous Investigations 2-7
2.2 NATURE AND EXTENT OF CONTAMINATION 2-9
2.2.1 Soils 2-9
2.2.2 Groundwater 2-9
2.3 CONTAMINANT FATE AND TRANSPORT 2-14
2.3.1 Organics Fate and Transport 2-142.3.2 Metals Fate and Transport 2-15
2.4 APPLICABLE SITE STANDARDS 2-16
2.5 EVALUATION BASIS FOR INTERIM RESPONSE ACTIVITY 2-17
3.0 IDENTIFICATION AND EVALUATION OF INTERIM ACTIONTECHNOLOGIES 3-1
3.1 INTERIM RESPONSE ACTION OBJECTIVE 3-1
312 IDENTIFICATION AND EVALUATION OF TECHNOLOGIES 3-1
3.2.1 Monitoring 3-23.2.2 Institutional Controls 3-23.2.3 In-place Containment 3-23.2.4 Source Collection Accession For 3-63.2.5 Treatment 3-63.2.6 Temporary Storage/Disposal -- 3-12
3.2.7 Dewatering and Water Treatment DTI C TAg -i-3-13
3.3 SUMMARY OF RETAINED TECHNOLOGIES J.u . 3-21
4 . A vai eb '11 1tY 00odes
-- Dint ) Spand r0a
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3 4.0 DEVELOPMENT AND EVALUATION OF ALITENA1IE 4-1
4.1 INTERIM ACTION ALTERNATIVES 4-1
4.1.1 Alternative 1 - No Action 4-24.1.2 Alternative 2 - Monitoring 4-24.1.3 Alternative 3 - Institutional Controls 4-34.1.4 Alternative ý - Slurry Wall with Cap 4-34.1.5 Alternative 5 - Multilayered Cap 4-44.1.6 Alternative 6 - In-situ Vitrification 4-44.1.7 Alternative 7 - Chemical Fixation with Onsite Storage 4-64.1.8 Alternative 8 - Chemical Fixation with Offsite Disposal 4-9
4.2 INTERIM ACTION EVALUATION CRITERIA 4-10
4.2.1 Overall Protection of Human Hcalth and theEnvironment 4-10
4.2.2 Conformance with ARARs 4-104.2.3 Reduction of Mobility, Toxicity, or Volume 4-10
4.2.4 Short- and Long-term Effectiveness 4-114.2.5 Implementability 4-12
35.0 ECONOMIC EVALUATION OF ALTERNATIVES 5-1
5.1 ECONOMIC ASSUMPTIONS 5-1
5.2 ALTERNATIVE COSTING 5-3
5.2.1 Alternative 1 - No Action 5-35.2.2 Alternative 2 - Monitoring 5-35.2.3 Alternative 3 - Institutional Controls 5-45.2.4 Alternative 4 - Slurry Wall with Cap 5-45.2.5 Alternative 5 - Multilayered Cap 5-55.2.6 Alternative 6 - In-situ Vitrification 5-55.2.7 Alternative 7 - Chemical Fixation with Onsite Storage 5-65.2.8 Alternative 8 - Chemical Fixation with Offsite Disposal 5-7
5.3 SENSITIVITY ANALYSIS 5-8
6.0 CONCLUSIONS 6-1
3 6.1 ALTERNATIVE SCREENING 6-1
6.2 ALTERNATIVE EVALUATION 6-4
S6.2.1 Alternative 4 - Slurry Wall with Cap 6-56.2.2 Alternative 5 - Multilayered Cap 6-56.2.3 Alternative 6 - In-situ Vitrification 6-66.2.4 Alternative 7 - Chemical Fixation with Onsite Storage 6-66.2.5 Alternative 8 - Chemical Fixation with Offsite Disposal 6-7
S6.3 CONCLUSIONS 6-7
7.0 REFERENCES 7-1
SAPPENDIX A - Comments and Responses A-1
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S UST Of-TABLES.
2-1 SUMMARY OF CONTAMINANTS IN SOIL AND SLUDGE 2-10
I 2-2 SUMMARY OF CONTAMINANTS IN GROUNDWATER 2-11
2-3 M-1 SETTLING BASINS EVALUATION BASIS 2-18
I 3-1 IDENTIFICATION OF POTENTIAL TECHNOLOGIES FOR SOILS AND SLUDGES 3-22
3-2 IDENTIFICATION OF POTENTIAL TECHNOLOGIES FOR WATER 3-28
P3-3 TECHNOLOGY SCREENING FOR SOILS AND SLUDGES 3-32
3-4 TECHNOLOGY SCREENING FOR WATER 3-36
4-1 TECHNICAL EVALUATION OF ALTERNATIVES - THRESHOLD CRITERIA 4-14
4-2 TECHNICAL EVALUATION OF ALTERNATIVES - EVALUATION CRITERIA 4-16
5-1 PRESENT WORTH SUMMARY TABLE 5-9
5-2 ALTERNATIVE 2 - GROUNDWATER AND AIR MONITORING - 5-10COST ESTIMATE
5-3 ALTERNATIVE 3- INSTITUTIONAL CONTROLS - COSTESTIMATE 5-11
5-4 ALTERNATIVE 4 - SLURRY WALL WITH CAP - COSTESTIMATE 5-12
5-5 ALTERNATIVE 5 - MULTILAYERED CAP - COST ESTIMATE 5-13
5-6 ALTERNATIVE 6 - IN-SITU VITRIFICATION - COSTESTIMATE 5-14
5-7 ALTERNATIVE 7 - CHEMICAL FIXATION WITH ONSITE STORAGE - COSTESTIMATE 5-15
5-8 ALTERNATIVE 8 - CHEMICAL FIXATION WITH OFFSITE DISPOSAL - COSTU ESTIMATE 5-17
5-9 SENSITIVITY ANALYSIS 5-18
6-1 ALTERNATIVE CLASSIFICATION 6-3
6-2 REDUCTION OF MOBILITY, TOXICITY, OR VOLUME EVALUATION 6-9
6-3 SHORT-TERM EFFECTIVENESS EVALUATION: COMMUNITYPROTECTION 6-11
S 6-4 SHORT-TERM EFFECTIVENESS EVALUATION: WORKER PROTECTION 6-12
6-5 LONG-TERM EFFECTIVENESS EVALUATION 6-13
III
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S LIST OF TABLES (Continued) Em
6-6 IMPLEMENTABILITY EVALUATION 6-15
3 6-7 COST EVALUATION 6-17
LIST OF FIGURES
1-1 M-1 SETTLING BASINS AND LIME SETTLING BASINS AREA MAP 1-2
1-2 DECISION FLOW CHART FOR INTERIM ACTION VERSUSMONITORING/MAINTENANCE ON HOT SPOT IRAs 1-4
2-1 M-1 SETTLING BASINS FIELD INVESTIGATION 2-8
6-1 IRA ALTERNATIVE RANKING 6-2
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1.0INTRODUCTION
1.1 PURPOSE OF THE IN'TERM RESPONSE ACTION (IRA) ALTERNATIVE ASSESSMENTDOCUMENT
The IRA Alternative Assessment Document describes the process and results of the alternative assessment
conducted for the M-1 Settling Basins at the Rocky Mountain Arsenal (RMA). The M-1 Settling Basins are
located in the South Plants area of RMA near December 7th Avenue, just east of D Street (Figure 1-1). The
M-1 Settling Basins are evaluated as being a direct source of arsenic contamination to the groundwater. This
evaluation is discussed in subsection 2.2.2.
Technologies and alternatives have been developed that will remove or contain the apparent source of
groundwater contamination at this site. These alternatives will be evaluated to assess whether there is a clear
and significant benefit in performing an interim response action now. The selection of the preferred interim3 action is presented in Section 6.0.
The interim response action referenced herein is identified in Section XXII of the Federal Facility Agreement,
paragraph 22.1 (1) and is governed by the process set forth in paragraphs 22.5 - 22.14 of that Agreement.
The goal of this assessment document is to evaluate alternatives based upon, but not limited to, factors such as
the protection of human health and the environment, mitigation of the threat of human health and the
reasonableness of cost and timeliness. Consistent with the Comprehensive Environmental Response,
Compensation and Recovery Act of 1980 (CERCLA), as amended by SARA, 1986, and the National Contingency
Plan (NCP), the assessment seeks to balance preferences for treatment on site and for responses that
permanently reduce the mobility, toxicity, or volume of hazardous substances against the need, in the context of
removal actions, for consistency with the final remedy and for responses that are practical, cost-efficient, and that
reduce or control hazards posed by the site as early as possible.
1.2 IRA CANDIDATE SELECTION CRITERIA
To evaluate whether and what type of response action is necessary and appropriate, the following questions have
been developed as part of a decision logic:
(1) Is the site an active primary source?
S• Is it an active source of groundwater contamination?
* Is it a primary groundwater contamination source?
I 1-1(11111CD2.3100) (11/18/89) (KMA)I
..- .Woudward.CClyde Cpn.ultants
LIME SETTLING BASINSI36076
36055
•., 36194 DENVER
5240.2' 0.-243.7'; -,, 36167j
CONTAMINATED 3058SEWER LINE5202
S~360545250.7
• 5 5252.6'
36001 R!5251.7' 36193
DECEMBER EMA-,.
01 015015 010775255.6' 2557
•]5256.5'
10835257.6*0 M-1 SETTLING BASINS
01524
S~LEGEND
30 CONTAMINATED SEWER LINE
0 100 200 400S• MONITORING WELL LOCATION
SCALE IN FEET NEW MONITORING WELL LOCATION
IJob o 23 Figure 1-1 M-1 SETTLING BASINS
Prelpored ty:- R.L.,C. AND LIME SETTLING BASINS/Dole: 9/21/69 AREA MAP AA"
1-2
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(2) Does the site pose a significant risk to human or biota receptors?* Have potential receptors been identified?
• Have previous studies been confirmed by new data?
* Is there any conflicting evidence?
(3) Is there a significant long-term benefit if an IRA is done now?
* Will interim action result in an accelerated cleanup?
* Will interim action reduce long-term costs?
The type of action taken and the timing of the action will depend on the responses to the above questions. The
decision logic is shown in Figure 1-2.
If the answers to the questions on the decision flow chart are inconclusive then reasonable yet conservative
assumptions favoring a protective response will be adopted.
The M-1 Settling Basins have been evaluated as being an active primary source of groundwater contamination.
Although this site does not appear to pose a significant risk to human or biota receptors at this time, there
appears to be both a long-term cost and technical benefit in performing an IRA now since treatment after the
arsenic has spread becomes both more costly and complex insofar as a larger area must be addressed.
Alternative interim response actions are discussed in this document. The benefit in performing any of these
actions is discussed in Section 6.0.
13 REPORT ORGANIZATION
This Alternative Assessment Document is divided into five additional text sections and a reference section.
Section 2.0 of this Alternative Assessment Document summarizes the information and results of the current and
previous investigations, including a brief description of the site, extent of contamination, and a summary of the
evaluation basis. Section 3.0 identifies and provides a preliminary evaluation of feasible interim action
technologies. Section 4.0 presents the alternatives developed from the feasible technologies, provides a detailed
description of each site-specific alternative, and describes the criteria used to evaluate the alternatives. Section
5.0 presents a cost estimate of each alternative. Section 6.0 presents an evaluation of the alternatives.
1-3(11111C02-3100) (11/18/89) (RMA)
II SITE C HARACTERIZATION]
I
IS SITEAN ACTIVE
PRIMARY NO MONITORING/
ISOURCE OR DATA INADEQUATE MAINTENANCE
U?
IIsIYE
POSE ASINFCTSIGNIFICANT RISK NO LN-EMCS
TO HUMAN AND ORTCHIA
U R
IIi
Job No 22238 Figure 1-2 - DECISION FLOW CHART FORPrepred y: DC.C.INTERIM ACTION VERSUS
P'epared by: D).C.C. MONITORING/MAINTENANCE
Dole: 6115/S9 ON HOT SPOT IRAs
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* 2.0SITE BACKGROUND AND INTERIM ACTION INVESTIGATION
I 21 SITE DESCRIPTION
I 2.1.1 Location
The M-1 Settling Basins are located in the South Plants area just south of December 7th Avenue alongthe northern edge of the northwest quarter of Section 1 at the Rocky Mountain Arsenal (RMA). The
northwest corner of the basins is 75 feet south of the centerline of December 7th Avenue and 25 feet
east of the contaminated sewer line that extended from the South Plants to the Lime Settling Basins
(Figure 1-1). The elevation of the ground surface in the M-1 Settling Basins area is approximately
5,265 feet above mean sea level (MSL). The basins and the berms surrounding them, all of which are
now buried and partially built upon, occupy an area of approximately 46,200 square feet.
I 2.1.2 History
Two basins were originally constructed in 1942, but when these filled with solids, a third was constructed
in 1943. All three were unlined, each measured approximately 90 feet wide (E-W), 115 feet long, and
7 feet deep, according to the as-built drawings. They were initially constructed to treat waste fluids from
the lewisite facility. However, lesser amounts of waste materials from alleged spills within the acetylene
generation building, the thionylchloride plant, and the arsenic trichloride plant may have been routed
Sftrough loor drains and the connecting piping to the basins (Ebasco Services, Inc. 1987).
The liquids discharged into the basins first passed through a set of re-.:tor towers where calcium
carbonate was added, then through a wooden trough into the M-1 Settling Basins where the arsenic
precipitated out of solution. The elutrate was decanted off through an 18-inch-diameter pipe to the3 Lime Settling Basins in Section 36 where final treatment occurred and then routed into Basin A (Ebasco
Services, Inc. 1987).
I The basins also received a considerable amount of mercuric chloride catalyst, possibly from a spill.
Various sources reported quantities such as 183,000 pounds, 500 pounds, 30,000 gallons, and $25,000
worth (Ebasco Services, Inc. 1988).
The basins were backfdled, probably in 1947, and are now covered with soil and some structures. Thefacilities that surround the M-1 Basins area were used in the manufacture of bicycloheptadiene until
1974.
2-13 (11111C02-3100) (11/18/89) (RMA)
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S2.1.3 G
3 This section describes the regional geologic setting at RMA and the site-specific geology at the M-1
Settling Basins.
2.1.3.1 Reiional Geoloa
The RMA is located about 7 miles northeast of central Denver in western Adams County. It occupies
approximately 27 square miles within the Colorado Piedmont section of the Great Plains physiographicprovince. The surficial deposits of this area are characterized primarily by a veneer of wind-deposited
and alluvial materials. Most of the topography at the Arsenal is gently rolling; however, there are several
prominent hills that contain outcrops of resistant bedrock (Costa 1982).
I The geologic history of the RMA and surrounding area spans at least 1-3/4 billion years and is recorded
by the rock units that underlie the RMA. The oldest rocks are Precambrian crystalline units that occur
approximately 12,000 feet below the surface. The youngest units are the Quaternary age surficialdeposits that blanket the RMA. Since the Precambrian, the area has experienced several advances and
withdrawals of shallow marine seaways, three episodes of orogeny (mountain building), and three periods
of relative crustal stability that preceded the orogenic episodes. The first orogenic episode began in the
Pennsylvanian period, the second in the Cretaceous, and the third, the Laramide Orogeny, occurredduring the late Cretaceous and early Tertiary periods. The Laramide Orogeny was responsible foruplifting the Front Range Mountains and down-warping the Denver Basin.
Following the Laramide Orogeny, relative crustal stability existed in the Eocene Epoch. Periods of
extensive erosion and deposition in late Eocene were followed by extensive volcanic eruptions during
the Oligocene. Then, during the Pleistocene, a cooler, wetter climate brought periods of glaciation tothe mountains (Hansen 1982). Regional uplift, mountain glaciation, stream erosion, and subsequent
deposition were responsible for the Quaternary deposits and shaping the present-day topography (Haun
1965).
I The Rocky Mountain Arsenal lies within the Denver Basin, one of the largest structural basins in theRocky Mountain region. It covers approximately 60,000 square miles in portions of Colorado, Nebraska,
Wyoming, and Kansas. The Denver Basin is an asymmetrical north-south trending syncline with its
structural axis close to and parallel to the Front Range. Rock units on the west flank of the basin dip
gently to the east though the dip becomes progressively steeper near the boundar, between the Front
Range uplift and the Denver Basin (Hansen 1982). The east flank of the basin generally dips to the westat one degree or less (Sonneberg 1982).
2-2S(11111C02-3100) (11/18/89) (•MA)
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5 The Denver Basin is filled with approximately 15,000 feet of sediments. Several major transgressions
followed by periods of emergence resulted in the deposition of both marine and continental sediments
(Haun 1965) consisting of conglomerate, sandstone, siltstone, shale, limestone, dolomite, coal, lignite,
and volcaniclastic sediments. The Laramide Orogeny marked the last retreat of the marine seaway and,
thu,, sediments from the upper Cretaceous and the lower Tertiary record the final regression of the3 inland sea (Weimer 1973).
1 2.13.2 Stratigrap.
The full stratigraphic section at the Arsenal was penetrated by a deep injection well drilled in Section
26 in 1961. The well, used for contaminated wastewater disposal, reached a total depth of 12,045 feet
in Precambrian basement rock. Injection of wastewater continued from March 1962 until September
1965. The operation was abandoned in 1965 after the injection of wastewater was correlated to an
abundance of earthquakes in the area (Evans 1966).
3 Lithologic information obtained from the well indicates that there are 11,950 feet of Cambrian to
Tertiary sedimentary rocks beneath the Rocky Mountain Arsenal. Unconsolidated Quaternary deposits
uncomformably overlie the bedrock formations. Within these sediments are several aquifers including
the Fox Hills sandstone of late Cretaceous age, the Laramie and Arapahoe Formations of late
Cretaceous age, portions of the Denver Formation of late Cretaceous and early Tertiary age, and theoverlying Quaternary surficial deposits (May 1982). The units of greatest concern at the RMA includeportions of the Denver Formation and the unconsolidated Quaternary surficial deposits.
2.1.3.3 Denver Formation
I The Denver Formation, which subcrops and occasionally outcrops at the Rocky Mountain Arsenal, was
originally as much as 900 feet thick, but due to subsequent erosion, it now ranges from 250 to 500 feet
Sat the Arsenal (May 1982). It was derived predominately from the erosion of andesitic and basaltic
rocks and was deposited in fluvial environments, and as lacustrine deposits on an extensive piedmont5 plain (Romero 1976).
Materials in the Denver Formation include olive-gray, brown, and green-gray interbedded claystone,
siltstone, sandstone, conglomerate, carbonaceous clay shale, low-grade coal, and lignite. Volcaniclastic
material is also present in the Denver Formation and consists of angular to subangular lithic fragments
and minerals in a fine-grained clay matrix. The clay matrix is bentonitic and is probably the weathering
product of volcanic ash (May 1982).
2-3(11111C02.3100) (11/18/89) (RMA)
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Individual aquifers within the Denver Formation range in thickness from several inches up to 60 feet.
They are generally discontinuous, lenticular, and consist of poorly cemented, medium- to fine-grained
sandstone, which grade vertically and laterally into siltstone and day shale (May 1982).
2.1.3.4 Ouaternarv Denosits
Unconsolidated sediments of Quaternary age uncomformably overlie the Denver Formation at the
Arsenal. There are, however, a few locations where bedrock is exposed at the surface near topographic
highs. The upper surface of the Denver Formation is a paleotopographic or erosional surface that was
incised by ancient stream channels. These paleochannels were filled by unconsolidated surficial deposits
(Costa 1982). The surficial deposits previously referred to as Quaternary alluvium or the alluvial aquifer
are up to 130 feet thick and consist of alluvium, loess, and eolian deposits. They have been subdivided
into eight units ranging in age from Pleistocene to Holocene (Scott 1960). At the Rocky Mountain
Arsenal, six units have been mapped. They are the Verdos alluvium of Kansan age, Slocum alluvium of
lllinoian age, Louviers and Broadway of Wisconsin age, Piney Creek alluvium, and Post-Piney Creek
3 alluvium of Holocene age (DeVoto 1968).
m 2.1.3.5 Alluvium
The alluvial deposits are generally composed of yellowish-brown to very pale orange days, silts, sands,
gravels, and boulders. Coarser alluvial material is found in the paleochannels (May 1982). The alluvium
is generally unconsolidated except where calcium carbonate has cemented sand and gravel into a
m conglomerate. The grain size of the alluvial material ranges from clay size to boulders. The sands are
subangular to subrounded quartz with mica, heavy minerals, and chert. According to the Unified Soil
Classification System, they are predominately SM (sand-silt mixtures) and SP (poorly graded sands) and
often contain gravel. The sands are lenticular and grade laterally and vertically into clay, silt, and gravel
(May 1982).
2.1.3.6 Loess/Eolian Deoosits
m Loess and other colian deposits of Pleistocene and Holocene age are widely distributed at the RMA.
The loess is generally less than 10 feet thick but may be up to 20 feet thick in the eastern part of the
area. It consists of yellowish-brown to light grayish-brown sandy silt and may contain large amounts of
clay. The other eolian deposits are generally 10 to 20 feet thick but may be as much as 40 to 50 feet
thick. They consist of light-brown fine sand, sandy silt, and clay (Lindvall 1980).
2-4(11111CO2-3100) (11/18/89) (RMA)
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2.1.3.7 Site GJl
The M-1 Settling Basins are located on a paleotopographic high near the headwaters of a series of
palcodrainages that originate in the upland area now occupied by Section 1. Two significant
stratigraphic units have been identified at the site. These are the Quaternary Alluvium and the
Cretaceous-Tertiary Denver Formation.
The surficial materials in the M-1 Settling Basins are 10 to 15 feet thick and unconformably overlie the
Denver Formation. The entire area around the basins is covered with a veneer of imported soil. The
soil cover over the waste material in the basins ranged from 2 to 4 feet thick.IThe unconsolidated alluvial material is composed of yellowish-brown to grayish-brown, fine-grained to
medium-grained, subangular, alluvial, eolian, and eluvial sands, silts, and clays, with some minor amounts
of gravel.
U The Denver Formation, to the depth penetrated, is composed of weathered, dark to dusky brown, hard,
dense, blocky claystone interbedded with medium-gray, hard, sandy to gravelly siltstone and lignite. The
contact between the alluvial unit and the Denver Formation is generally characterized by a claystone;
however, it may also be marked by siltstone or lignite. The elevation of the contact between the alluvial
soil and the top of the Denver Formation is variable at RMA. In the M-1 Settling Basins area, the
contact was found between an elevation of approximately 5,246 and 5,254 feet above MSL (Ebasco
Services, Inc. 1989a).
1 2.1.4 Hvdrolotv
This section describes the regional hydrologic setting at RMA and the site-specific hydrology at the
M-1 Settling Basins.
2.1.4.1 Regional Hydrology
5 The Rocky Mountain Arsenal lies within the South Platte River drainage basin. The river is located
several miles to the west and northwest of the Arsenal.
Several tributary drainages flow northwest across the Arsenal to the South Platte River. Groundwater
at the Arsenal occurs in the Quaternary surficial deposits and in several bedrock aquifers. The aquifers
of primary concern at the Rocky Mountain Arsenal, however, are the Quaternary deposits and portions
of the underlying Denver Formation. The deeper bedrock aquifers are apparently separated from the
p 2-5(11111CO2-3100) (11/18/89) (RMA)
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Denver Formation by 50 to 100 feet of shale called a *buffer zone,* which acts as an aquitard (Romero
1976).
U Groundwater at the Rocky Mountain Arsenal generally flows from the southeast to the northwest and
eventually discharges into the South Platte River. There are local variations in flow direction (May 1982).
One such variation is caused by the local bedrock paleotopography and the groundwater mound that
exists beneath the South Plants area in Section 1 (May 1982). Groundwater in the unconsolidated
Quaternary alluvial aquifer is found under unconfined conditions. Groundwater in the Denver
Formation is found under unconfined and confined flow conditions at the Arsenal. The nature of the
contact between the alluvial aquifer and the Denver Formation may determine whether the flow
conditions in the Denver Formation are unconfined or confined. If Denver Formation sandstones
subcrop below the saturated alluvium, the base of the subcropping sandstone is considered the base of5 the unconfined ' system.
The hydraulic conductivity of the two aquifers varies considerably. The hydraulic conductivity of the
alluvium has been measured at between 9.08 x 101 to 2.4 x 10"3 cm/sec. The lower hydraulic conductivity
values were found in the Basin A area. Hydraulic conductivity measured in the Denver Formation
yielded values ranging from 10' cm/sec for clay shales to 10*3 cm/sec to 10' cm/sec for sandstones
(May 1982).
I Due to the contrast in hydraulic conductivity between the Denver Formation clay shales and the
alluvium, groundwater flow and contaminant transport through unfractured bedrock is assumed to be3 relatively slow compared to flow and transport in either saturated alluvium or in fractures or sandstones
in the Denver Formation (Stollar 1988). Within the alluvial unit, the paleochannels generally have higher
hydraulic conductivities than the surrounding alluvial materials due to the coarser materials in the
paleochannels. These channels appear to serve as conduits that move alluvial groundwater at higher
rates and volumes than in other parts of the unconfined system (May 1982). The primary groundwater
flow components at the Arsenal generally follow the paleochannels in the alluvium; however, flow is not
restricted to only the paleochannels. Groundwater flow does occur over channel divides and through
the Denver Formation (May 1982).
2.1.4.2. Site Hydrology
Both the alluvial and bedrock units are known to be water-bearing units in the M-1 Settling Basins area.
Previous investigations conducted at RMA have concluded that the alluvial aquifer is unconfined and
that the Denver Formation may be partially confined in some zones beyond the upper weathered zonep (Ebasco Services, Inc. 1989b). The weathered portion of the Denver Formation is apparently in contact
2-6l (1111CO2-3100) (11/18/89) (RMA)
I
I Woodwardcd. Conmuftants
3 with the alluvial aquifer. Since this investigation focused primarily on evaluating impacts to the alluvial
aquifer, the discussion will be limited to the characteristics of the unconfined alluvial aquifer.
I In the M-1 Settling Basins area, groundwater flow in the alluvial aquifer is apparently toward the north
and possibly slightly northwest due to the influence of localized njounding of groundwater in the South3 Plants area. The local groundwater gradient is in the range of 0.008 to 0.011 ft/ft. Due to seasonal
variations and local topography, the top of the groundwater ranges from approximately 5 to 10 feet
below ground surface. The average saturated thickness of the alluvial aquifer is approximately 8 feet.
Aquifer tests conducted on the alluvial aquifer during previous investigations at RMA indicate that the
hydraulic conductivity of the unit is in the 6.0 x 10"3 cm/sec to 2.4 x 10- cm/sec range. By comparison,
the reported hydraulic conductivity value for the Denver Formation is iu the range of 5 x 10s cm/sec.
I 2.1.5 Previous Investigations
2.1.5.1 Soils
The M-1 Settling Basins were investigated by the Army's consultant, Ebasco, in 1987 and by Shell's
consultant, Morrison-Knudsen Engineers in 1988. Twenty-six soil and waste samples were taken from
6 borings within or near the M-1 Settling Basins during the two investigations. The locations of these
borings are shown in Figure 2-1. The samples were analyzed for volatiles, semivolatiles, ICP metals,
arsenic, mercury, and thiodiglycol.
I 2.1.5.2 Groundwater
I Several groundwater monitoring wells have been installed to monitor alluvial groundwater in the vicinity
of the M-1 Settling Basins. Well Nos. 01503 and 01504 are located in the berm immediately
downgradient of the M-1 Basins, Well No. 01524 is located approximately 100 feet upgradient of the
western-n.-st basin, Well No. 36001 is located approximately 200 feet northwest (downgradient) of the
western-most basin, and Well No. 01077 is located approximately 100 feet east of the basin area. The
locations of these wells are shown in Figure 2-1. Samples from the wells were analyzed for total and
dissolved arsenic, mercury, volatiles, semivolatiles, and pesticides during previous investigations. In
spring 1989, Well Nos. 01503, 01504, 01524, 01077, 36001, and new Well Nos. 01083 and 36193 were
sampled and analyzed for total and dissolved arsenic and mercury.II
2-7(11111C02-3100) (11/18/89) (RMA)
I
I p,38 Woodward.Clyde Consultants
3 01077
SCALE: 1" - 60'
,-FENCE AND STEAM LINE
UoWCC -5
wcc-6e
0 1504 3 SS-4
GENERALIZED GROUNDWATER FLOW
WCC-4
NRSO1M1E
I I 7 01083
1 0NRS01NIM
055-536193
WCC-6WCC-3 '4 01503 NRSO1NIW WCC-1
WCC-2
LEGEND 01524-+ EXISTING WELL3 NEW WELL
S11 FOOT DEEP BORING19 FOOT DEEP BORING
"RS-EO SOIL BORING (NATURAL RESOURCES)E 36001 IS-1 0 SOIL BORING (ARMY SPILL SITE BORING)
job No.: 22238 Figure 2-1 M-1 SETTLING BASINS
Prepared by: R.L.C. FIELD INVESTIGATIONS
2-8
* Woodwadc C uants
52.2 NATURE AND EXTENT OF CONTAMhNATION
5 2.2.1 S
Soil samples collected and analyzed during investigations of the M-1 Settling Basins indicated high
concentrations of arsenic and mercury in the soil in and around the basins at depths of 0.5 foot to
approximately 7.0 feet. The concentration of arsenic and mercury in samples taken within the basins
was variable and ranged from 0.01 to 11.0 percent. Concentrations of these constituents are reduced
at depths below approximately 7 feet and in the soil surrounding the basins. Table 2-1 shows a summary
of the contaminants found in soil samples taken during the previous studies.
2.2.2 Groundwaier
Groundwater samples taken and analyzed during previous investigations showed a difference in the
concentration of arsenic between filtered and unfiltered groundwater samples from wells immediately
downgradient of the basins. Unfiltered groundwater samples from Well Nos. 01503 and 01504 indicated
up to 59,000 ug/l arsenic, while the filtered samples indicated less than 0.01 ug/! for each well. The
Sexplanation for this difference is unclear. It has been suggested that a high concentration of arsenic is
attached to soil particles moving with the groundwater as it leaves the M-1 Settling Basins area.
I Analytical results from groundwater sampling conducted in spring 1989 confirm that there are high levels
of arsenic in the groundwater, but these results show little difference between filtered and unfiltered
samples (WCC 1989). Total and dissolved arsenic concentrations are quite similar in magnitude and
indicate a high concentration of arsenic immediately downgradient of the M-1 Settling Basins. One
possible explanation for the difference between the filtered/unfiltered samples in previous investigations
versus the similarity in filtered/unfiltered samples in the 1989 investigation is that different sample
preservation methods may have been used. In either case, the high concentrations of arsenic
downgradient of the M-1 Settling Basins clearly indicate that this site is a direct source of arsenic
contamination to the groundwater. Table 2-2 is a summary of the contaminants found in groundwater
* from wells in the M-1 Settling Basins area.
III
2-9(1111tC02-3100) (11/18/89) (RMA)
I
I wooAward.-Cyde Consultants
TABLE 2-1
SUMMARY OF CONTAMINANTS IN SOIL AND SLUDGE
ISOIL SLUDGE
No. of Range No. of RangeContaminant Indications (ug/g) Indications (ug/g)
IVolatile Organic Compounds/GCMS
Methylene Chloride (CH2CL2) 3 3.42-6.70 4 3.0-6.1Bicycloheptadiene (BCHPD) 6 1.8 -5000 5 0.51.600
Semivolatile Organic Compounds/GCMSAidrin (ALDRN) 2 2.0-30Dicyclopentadiene (DCPD) 6 60-4000 6 1.4-60Dicedrin (DLDRN) 5 0.4-100Hexachlorocyclopentadiene (CL6CP) 1 3000Isodrin (ISODR) 1 10
Metals/ICPCadmium (Cd) 7 1.3-31.0 9 7.86-3900Chromium (Cr) 14 9.86-23 2 7.4-8.42Copper (Cu) 14 7.2-21 2 9.0-21.8Lead (Pb) 12 13-64 11 16.4-2483 Zinc (Zn) 7 39-76 7 16.1-70.7
Separate AnalysesArsenic (As) 14 9.2-1300 12 17,000-110,000Mercury (Hg) 11 0.33-210 12 400-9,400
I Sources:
RMA Data Base, August 1989Ebasco Services, Inc. 1988Woodward-Clyde Consultants 1989
1III
2-10(111IC02-3100) (11/18/89) (R%%A)
I
] WooclwardClyde Conaultant
TABLE 2-2U SUMMARY OF CONTAMINANTS IN GROUNDWATER
No. of Upgradient No. of DowngradientIndications (Well Nos. 01083 Indications (Well Nos. 01503,
01524, 01077) 01504, 36001,Range (ug/l) 36193)3 Range (ug/l)
Volatile Organic Compounds/GCMSBenzene (C6H6) 4 406-3,400 9 22-32,500Bicycloheptadiene (BCHPD) 3 13.2-74.0 4 2,379-9,500Carbon Tetrachloride (CCLA) 2 62.0-74.0 1 230.0Chlorobenzene (CLC6H5) 2 1,073-35,000 6 25-40,500Chloroform (CHCL3) 3 6.0-250 9 30.0-425,000Dibromochloropropane (DBCP) 2 4.5-7.74 -.
Methylisobutyl Ketone (MIBK) 3 10.0-7,200 5 6.9-3,063Xylene (XYLEN) 1 12.0 2 7.0-1,150Tetrachloroethene (TCLEE) 4 317.0-1,100.0 4 3.0-630.0Toluene (MEC6H5) 4 320.0-1,200 7 1.7-2,600
Dichloroethene (12DCLE) 1 690.0 1 2,300Trichloroethene (TRCLE) 3 331.0-1,500 6 1.9-2,250Dichlorobenzene (DCLB) -.... 3 5.6-5,500Methylene Chloride (CH2CL2) -- 2 380-1,250
SSem ivolatile Organic Compounds/GCM SAldrin (ALDRN) 3 0.29-3.1 2 0.75-1.58ChlorophenylmethylSulfide (CPMS) 2 89.0 -140.0 5 13.4- > 300
ChlorophenylmethylSulfoxide (CPMSO) 1 17.0 4 21.5- > 300
ChlorophenylmethylSulfone (CPMSO2) 3 20.9-28.2 7 20.1-160
Dibromochloropropane (DBCP) 2 4.5-7.74 4 76- > 300Dicyclopentadiene (DCPD) 1 330.0 15 97-84,200Dieldrin (DLDRN) 2 0.325-0.355 3 1.26-820.0Diisopropyl methylPhosphonate (DIMP) 1 33.5 9 3.0-6,600
DimethylmethylPhosphonate (DMMP) 2 12.6-45 1 130
Dithiane (DITH) 1 1.96 1 8.6Endrin (ENDRN) 2 1.40-5.9 2 0.71-1.53
Hexachlorocyclopentadiene -- . -- -...
(HCPD)Isodrin (ISODR) 1 0.252 2 2.0Atrazine (ATZ) -- - 1 1903 Phenol (PHENOL) .... 3 7.6-28
II
2-11I (11111C02-3100) (11/18/39) (RMA)
I
WoodwardClyde Conultants
3 TABLE 2-2 (Continued)
No. of Upgradient No. of DowngradientIndications (Well Nos. 01083, Indications (Well Nos. 01503,
01524, 01077) 01504, 36001,Range (ug/I) 36193)
Range (ug/I)
Organochlorine Pesticides (GCEC)Dichloroethane (PPDDE) 1 0.86 2 0.317-.551Trichloroethane (PPDDT) 2 0.790-1.5 3 0.454-
Organochiorine Pesticides (GCEC) (Cont)Aldrin (ALDRIN) 5 0.167-9.09Hexachlorocyclopentadiene (CLGCP) 5 0.721-38.6Endrin (ENDRN) 4 0.264-3.95Isodrin (ISODR) 4 0.223-2.3Chlordane (CLDAN) 3 2.62-19.7Dieldrin (DLDRN) 2 0.0774-2.77
Organosulfur Compounds/GCFID
Dimethyldisulfide (DMDS) 2 3.16-140Chlorophenylmethyl Sulfide (CPMS) 3 > 50-990Chlorophenylmethyl Sulfoxide (CPMSO) 3 32-36.6Chlorophenylmethyl Sulfone (CPMSO2) 3 > 100-1,080
Benzothiazole (BTZ) 2 19.4-22.2Dithane (DITH) 2 1.56-1.671,4-Oxathiane (OXAT) 1 3.34
Metals/lCPCopper (Cu) 1 44.8
m Zinc (Zn) 1 24.2
DIMP/DMMPDiisopropylmethyl Phosphonate (DIMP) 2 58.8-72.9Dimethylmethyl Phosphonate (DMMP) 5 1.39-1,100
ArsenicPrevious Investigations
Total 2 23,400-59,300Filtered 2 0.0058-0.0063
1989Total 2 7.15-10.30 7 18.6-19,700Filtered 2 3.01-6.36 7 2.57-12,900l
U
£ 2-12(11111C02-3100) (11/18/39) (RMA)I
I
Woodward.Clyde ns wtt
3 TABLE 2-2 (Continued)
No. of Upgradient No. of DowngradientIndications (Well Nos. 01083, Indications (Well Nos. 01503,
01524, 01077) 01504, 36001,Range (ugA) 36193)
Range (ug/l)
MercuryPrevious Investigations 0.164
1989Total 1 0.132 6 1.93-16,600Filtered .. --- 6 2.45-16,600
U Sources:
RMA Data Base, August 1989WCC 1989
2-13(1111Co2.3100) (11/18/89) (RMA)
S Woodward-Clyde ComuLtants
S2.3 CONTAMINANT FATE AND TRANSPORT
The contaminants observed in the field investigation can exist in several chemical forms in the environment
and can progress through several media in a uumber of different ways. This section presents the fate and
transport of both the predominant organics and metals detected in the soils and sludges during these field
Sinvestigations. First, the fate and transport of the predominant organic compounds will be discussed. This
will be followed by a discussion of the fate and transport of metals detected at the M-1 Settling Basins.
1 2.3.1 Organics Fate and Transnort
3 Although the sludge material and the overburden soil at the M-1 Settling Basins contain several organic
compounds in trace amounts, two organic compounds are present in concentrations as high as four orders
of magnitude above their detection limits: bicycloheptadiene and dicyclopentadiene. These compounds will
be the focus of this section. Based on the chemical and physical properties of these compounds and on
previous fate and transport studies (Ebasco Services, Inc. 1987), se'veral observations can be made:
0 Since previous investigations only detected these compounds at depths greater than1 4 feet, the volatilization of these compounds is probably negligible.
0 Neither compound shows appreciable bioconcentration. This, in addition to the fact that only
minimal plant life exists at the site, makes plant uptake and subsequent bioconcentration aminor fate mechanism.
0 Microbial degradation of these compounds has been reported to occur. However,
given the high arsenic concentrations of the sludge, microbial activity in the sludge
material will be minor. If other transport mechanisms remove the compounds from
this high arsenic concentration environment into an area that is sustaining microbial
Sactivity, some subsequent degradation of these compounds Will occur.
0 Both compounds will be sorbed on to the sludge material and on to the local
sands and silty sands. However, both compounds are susceptible to subsequentdesorption and transport with the alluvial groundwater. This mechanism is likely
during periods of high groundwater levels, when the alluvial groundwator extends
into the sludge material. Since two orders of magnitude increase in the
concentration of these compounds is observed in groundwater downgradient,
I2-14S(11111C02.3100) (11/18/89) (RMA)
I
Woodward Clyde ConultantsIrelative to upgradient, of the M-1 Settling Basins (Table 2-2), it appears that
some desorption and subsequent transport with the alluvial groundwater is
occurring.
In summary, bicycloheptadiene and dicyclopentadiene appear to be sorbed on to the sludge material and
on to the local sands and silty sands. During periods of high groundwater, the compounds are desorbed
into the alluvial groundwater and are transported downgradient. These compounds will then slowly3I degrade to more stable compounds as they migrate into areas of increased microbial activity.
2.3.2 Metals Fate and Transport
The primary metal contaminants of concern at the M-1 Settling Basins are arsenic and mercury. The
contaminant assessment report also shows occasional, isolated, elevated concentrations of cadmium.
Although arsenic and mercury are present throughout the study area and will be the focus of the
discussion, cadmium will also be discussed. A review of the major fate area and transport mechanisms
of these compounds (Ebasco Services, Inc. 1987) allows for the following observations:
* Arsenic is mobile in the environment and may be present in several chemical forms (e.g.,
arsenate in oxidizing environments and arsenite in reducing environments).
U Biomethylation would occur for both arsenic and mercury, if conditions for aerobic activity
were present (e.g., large numbers of bacteria, large amounts of organic material and5nutrients, neutral pH, moisture, etc). Biomethylation would form volatile methylarsenics and
organomercury compounds. These compounds would volatilize, if present at the near
surface, to undergo subsequent photolysis or washout in the atmosphere. Since conditions
at the M-1 Settling Basins are not conducive to significant aerobic activity and since a large
fraction of the metals are present at depths greater than "near-surface," biomethylation and3 subsequent volatilization is probably not an important fate and transport mechanism.
Mercury is readily sorbed onto soils. It is not readily leached from either organic-rich ormineral-rich soils. There is little plant life at the site; therefore, mercury uptake by plants
will be minor. Mercury can be remobilized by microbial conversion to its methyl and
dimethyl forms. However, since conditions are poor for microbial activity, this mechanism
is probably minor.I2-153 (111IIC02-3100) (11/18/89) (RMA)
I
Woodward-Clyde Consultants
" Leaching of arsenic off of soil and sludge particles would be limited by the sorption of
arsenic onto clays with high iron and aluminum oxide content. Since the predominant soil
types at the site are sands and silty sands, the arsenic could be leached into and transported
with the alluvial groundwater, either as an arsenate or arsenite.
" Cadmium is mobile in aquatic environments. It can be removed from aqueous media by
complexing with organic material. Its solubility and subsequent mobility in water is a
function of, among other factors, its oxidation state and pH.
" Cadmium can be readily concentrated into vegetable plant matter. However, these
concentration effects may be confounded by the phytotoxic effects of cadmium. Since plant
life in the area is minimal, it is assumed that the bioconcentration through plant material is
minor.
Based on the above observations, it appears that most of the metals present in the soils and sludge at
the M-1 Settling Basins are sorbed to the local sands and silty sands as well as the sludge material at
the site. Arsenic and some cadmium can be leached and transported with the alluvial groundwater.
Leaching and subsequent transport of mercury will be limited.
2.4 APPLICABLE SITE STANDARDS
With the available knowledge of the nature and distribution of chemical contaminants at the site, as well
as the fate and transport of these chemicals in the environment, a survey of applicable or relevant and
appropriate requirements (ARARs) is necessary. These ARARs will identify any site-specific regulatory
requirements that might limit the choice of alternatives. Action-specific and chemical-specific ARARs
are considered to the extent that any alternative which cannot potentially meet those requirements will
not be carried forward. Site-, action-, and chemical-specific ARARs will be finalized and issued
together with the decision document to identify those requirements which will guide the design and
implementation of the selected alternative.
2-16(1211C02-3100) (11/18/89) (RMA)
5 Wod dCtyde Consuftants
2.5 EVALUATION BASIS FOR INTERIM RESPONSE ACTIVITY
This section summarizes the engineering constraints considered in the technology and alternative
evaluation process.
The total areal extent of the three M-1 Settling Basins is shown to be 115 feet by 300 feet on designdrawings. It is assumed that the waste material in the basins is covered by 2 feet of sodl overburden and
that the waste material extends to a depth of 7 feet below ground surface. The total volume of the
sludge is estimated to be approximately 6,400 yd3.
Volume estimates for the sensitivity analysis consider only a maximum-volume case by assuming a 20-
foot perimeter boundary of soil to be treated around the M-1 Settling Basins. In addition, for the
sensitivity analysis, the depth of contamination was assumed to be 10 feet below ground surface.
Alluvial groundwater is assumed to be present at approximately 8 feet below ground surface, with some
seasonal variation. A low permeability or confining layer is assumed to be present about 15 feet below
ground surface. All treatment technologies will address the contents of the basins and the overburden
only. No aquifer dewatering and subsequent treatment is assumed to be necessary for the purpose of
excavation for this interim response action. Any excavation activities will be performed during the dry
season in late summer or early fall to reduce the potential for encountering groundwater.
Preliminary analysis of the waste material in the basins indicates that the in-place waste is approximately
47 percent water. The waste is described as a gray-to-white very wet, silty clay-like material, similar to
the consistency of toothpaste. Based on investigations, this material is assumed on the average to be
about 8 percent arsenic, 0.5 percent mercury with the balance being calcium oxide or calcium carbonate
as measured on a dry basis. The wet density of this material is assumed to be 135 tons/yd3
The soil surrounding the basins is gravelly to silty sands, with lesser amounts of clayey sands to siltysand. The in-place density of this soil is assumed to be 1.5 tons/yd&.
A summary of the evaluation basis is shown in Table 2-3.
2-17(11111C02.3100) (11/18/89) (RMA)
Woodward-Clyd Consutants
TABLE 2-3M-1 sE17rLING BASINS
EVALUATION BASIS
Site Characteristics
Perimeter ft 830 910Surface Area ft2 34,500 46,200Depth of Contamination ft 7 10Depth of Groundwater ft 8-9 10Depth of Confining Layer ft 18 18Volume yd3
Sludge 6,400 6,400Soil 2,600 10,700Total 9,000 17,100
Sludee Characteristics Soil Characteristics
Gray-to-white, very wet silty clay like Gravelly-to-silty sands, with lesser amounts of clayeymaterial sand to silty sandDensity: 1.35 tons/yd3 Density: 1.5 tons/yd3
3 Soil SludgeContaminant Geometric Mean (ug/g) Geometric Mean (ug/g)
Volatile Organic Compounds/GCMSMethylene Chloride (CH2CL22) 3.5 3.7Bicycloheptadiene (BCHPD) 235 45
Semivolatile Organic Compounds/GCMSAldrin (ALDRN) 8Dicyclopentadiene (DCPD) 1340 8Dieldrin (DLDRN) 4Hexachlorocyclopentadiene (CL6CP) 3000Isodrin (ISODR) 10
Metals/ICPCadmium (Cd) 3.6 22.9Chromium (Cr) 11.9 9Copper (Cu) 12.6 17.7Lead (Pb) 26.5 42.7Zinc (Zn) 61 35.1
Separate Analyses/AAArsenic (As) 78 38300Mercury (Hg) 6 2550
2-18(1111ICO2.3100) (11/18/89) (RMA)
SWoodward.ctyde Conultants
IDENTIFICATION AND EVALUATION OF INTERIM ACTION TECHNOLOGIES3.IThis section presents the interim action objective and identifies potential interim action technologies
specific to the M-1 Settling Basins at the Rocky Mountain Arsenal (RMA). As the pre!ininary step to
identifying interim response action (IRA) alternatives, potentially applicable technologies for the IRAs
are identified, descnrbed, and evaluated in terms of their feasibility and general effectiveness. Acceptable
technologies or combinations of technologies are developed into the IRA alternatives presented in
Section 4.0.
m 3.1 INTERIM RESPONSE ACTION OBJECTIVE
3 The objective of this IRA is to mitigate the threat of releases from the M-1 Settling Basins. Alternatives
to meet this objective are developed using technologies discussed in Section 3.2 and evaluated in SectionsIm 4.0 and 6.0. The evaluation is based on, but not limited to, such factors as protection of human health
and the environment, mitigation of the threat to human health, and the reasonableness of cost andg timeliness, per the Federal Facility Agreement (FFA), paragraph 22.6.
3.2 IDENTIFICATION AND EVALUATION OF TECHNOLOGIES
This section identifies and evaluates IRA technologies applicable to the M-1 Settling Basins. Tables 3-1
and 3-2 (tables are located at the end of this section) list general response actions and technologies
typically applied to contaminated soil and associated groundwater, respectively. Each technology is
evaluated as being applicable or not applicable, based on the site-specific and contaminant-specific
3 conditions at the M-1 Settling Basins.
The technologies remaining after this initial evaluation are then described in this section. This
description focuses on the technical performance, operational reliability, and implementation of each
technology. Several technologies are eliminated from further consideration at this point. Tables 3-3
3 and 3-4 summarize this discussion.
Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as
amended by SARA, 1986, guidance (Environmental Protection Agency 1988) suggests the selection of
no more than 10 or 11 alternatives. The alternatives should include a mix of institutional controls,
containment, in-situ treatment, and onsite treatment technologies, as well as onsite storage and offsite
disposal. This suggested mix of technologies was applied in selecting the alternatives described in
3 Section 4.0.
3-1(11111Co2.310o) (11/19/39)
Woodward-Clyde Consultants
This section is organized by general response action. Technologies are introduced with respect to their
applicability to address a particular general response. These general response actions include
monitoring, institutional controls, containment, source collection, treatment, and storage/disposal.
3.2.1 Monitorin
Monitoring of the M-1 Settling Basins would consist of periodic sampling of upgradient and
downgradient groundwater monitoring wells. Groundwater would be analyzed for the organic and
inorganic compounds that have been detected in the sludge and contaminated soil in the vicinity of the
M-1 Settling Basins. The historical data base, augmented by current and future monitoring, would
provide an indication of whether the M-1 Settling Basins are a continuing source of groundwater
degradation in the time between the implementation of this IRA and the overall site remediation.
Monitoring is a feasible technology at the M-1 Settling Basins.
3.2.2 Institutional Controls
Although not a technology, institutional controls are incorporated into the assessment as a variation of
the no action altcrnative. Institutional controls would be applicable in the case of no-action, onsite
storage or landfill, capping-in-place, or other interim alternatives that result in leaving contaminated
materials on site that could be compromised by future excavation or construction activities.
Since a fence and guard post are used to secure the arsenal, site access restrictions are in place to some
extent. Additional restrictions, such as fencing around the perimeter of the M-1 Settling Basins, would
be feasible.
3.2.3 Jn-place Containment
Six technologies are identified as either source containment or associated with source containment
measures:
"* Capping
* Dikes and berms
"* Slurry walls
"• Grout curtain"* Sheet piling
3-2(11111C02-3100) (11/18/89)
P WoCdward.lyde Comnsutants
5 Groundwater interception and treatment
3.2.3.1 CapDin.
1 Capping is a process used to cover buried waste materials to prevent their contact with the land surface
and surface water. Substantive performance standards for caps must conform with 40 CFR Part 264.310.
As described there, a cap consists of a compacted clay layer, a synthetic geomembrane liner, a sand
drainage layer, and a surface layer of vegetated topsoil, asphalt, or rock. For short-term implementation,3 non-conforming caps are sometimes applicable. These consist only of a compacted clay layer beneath
a surface layer of either vegetated topsoil, asphalt, concrete, or rock.
UI Surface caps must be sloped to provide rapid surface drainage away from the contaminated areas.
Collection systems may be incorporated into surface caps; however, this is generally not necessary if high
concentrations of mobile contaminants are not present. The technology required to implement this
alternative is commonly used for in-place closure of contaminated soils or in conjunction with3 confinement of contaminated groundwater.
Capping is effective in minimizing the leaching of contaminants from the soil profile above the
Sgroundwater table. However, waste materials below the water table will still be transported by
groundwater migration. Supplementary groundwater control measures are generally required when3 soil contamination extends below the groundwater table.
Surface-capping technology is relatively economical to implement, is technically feasible and, when used
in conjunction with other groundwater measures, can be effective in reducing contaminant leachate
production from near-surface soils.
3 3.2.3.2 Dikes and Berms
Dikes and berms are well-compacted earthen ridges constructed immediately upslope from, or along the
perimeter of, a disposal site. These structures are generally designed to provide short-term protection
of critical areas by intercepting storm r !i off and diverting the flow to natural or man-made drainage
ways.
3 This technology is a cost-effective, technically feasible method of preventing surface runoff from
impacting remediation operations at the M-1 Settling Basins.
(3-3
(11n1tC02-3t00) (11/18/89)
Woodward. Comamsb
3.2.3.3 Slurry Walls
A slurry wall is a vertical, low-permeability wadl, typically constructed of a soil-bentonite mixture, which
is placed in a trench kept open by a slurry (bentonite-water mixture). The trench is typically 2 to 3 feet
wide and is usually keyed into a low-permeability basal unit. A surface capping system is generally
constructed in conjunction with the slurry wall.
At this site, low permeability strata of the Denver Formation, which could effectively impede downward
migration of contamination, occur at a relatively shallow depth. These conditions are favorable for
economical soil-bentonite slurry wall construction. Excavation to the depth for the desired key into the
Denver Formation could be accomplished in a single stage by using a backhoe or similar excavation
equipment. Slurry wall construction has been performed successfully on other projects under similar
conditions and is an accepted method for groundwater or soil contamination containment.
The technology required for slurry wall construction is commonly used in containment of hazardous
waste sites. Because of the shallow depth to a low-permeability stratum and generally favorable soil
conditions, this technology is feasible for the M-1 Settling Basins. It is relatively economical to
implement and may be used in conjunction with a surface capping system or other groundwater control
measures as an effective measure of reducing contaminant migration.
3.2.3.4 Grout Curtain
Grout curtains are subsurface barriers created in unconsolidated materials by pressure injection. Grout
curtains are generally more expensive than slurry walls, and their ability to develop a continuous low-
permeability barrier is questionable. It has been shown that occasionally, as a result of grout shrinkage
and erratic movement of the grout through the soil pores, large voids may remain. Sandy soils present
at the site could require large volumes of grout, making this alternative potenti.ally very expensive with
less control of barrier wall continuity compared to a soil-bentonite slurry wall. For these reasons, this
technology is eliminated from further consideration.
3.2.3.5 Sheet Piling
Sheet piling cut-off walls may serve as a groundwater barrier to redirect groundwater flow. Such cut-
off walls may be used to redirect or contain groundwater to eliminate contact with contaminated
materials and/or to prevent contaminated groundwater and waste material from migrating off site. Of
the three available materials for sheet pilings (wood, precast concrete, and steel), steel is the most
efficient and cost-effective groundwater barrier.
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The installation of a steel sheet piling cut-off wall requires that the pilings be assembled at their edge
interlocks before being driven into the ground. The piles are then driven a few feet at a time over the
entire length of the wall, using either a pneumatic or steam pile driver, until the appropriate depth is
obtained.
Initially, steel sheet piling cut-off walls are quite permeable; the edge interlocks must be loose to
facilitate the driving process and to allow water to pass through them easily. Eventually, fine soil
particles may adhere within the seams, and thus, the wall becomes less permeable to groundwater flow.
In very coarse, sandy soils, the wall may never seal unless the piling seams are first grouted, which adds
to the overall cost. Corrosion of the steel from chemical exposure due to soil and groundwater con-
taminants can be reduced by the use of galvanized steel or other steel coatings at an increased cost;
however, driving operations may damage the coating material. In general, steel sheet piling cut-off walls
tend to be more expensive and probably less effective than slurry walls. Therefore, the use of sheet
piling cut-off walls is not considered a feasible interim action technology and is eliminated from further
consideration.
3.2.3.6 Groundwater Interception and Treatment
A successful containment technology that has been used at RMA is groundwater interception and
treatment. Groundwater extraction wells are pumped to create a reverse hydraulic gradient, thereby
limiting the migration of contaminants by reducing the movement of the groundwater. Extracted water
is treated and reinjected.
Groundwater extraction and treatment as a containment technology is usually used in conjunction with
a slurry wall. The slurry wall can either be constructed perpendicular to the groundwater gradient,
downgradient of the contaminant source, or it can be constructed 360" around the entire source area.
When the slurry wall is constructed downgradient of the source, the groundwater is extracted upgradient
of the well to maintain a reverse hydraulic gradient. When the 360 slurry wall is constructed, water
is extracted from inside it. Creating a lower potentiometric surface inside the slurry wall prevents
exfidtration of the groundwater through the slurry wall, which could result from possible construction
imperfections. This technology has been successfully implemented at several sites at RMA; however,
because other containment technologies are available for this site that do not require long-term
operations or the handling of secondary waste streams (specifically arsenic sludge from the water
treatment), it will not be considered further for the M-1 Settling Basins.
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3.2.4 Source Collection
Excavation of contaminated soils is a standard approach to source collectioa at hazardous waste sites.Excavation is a prerequisite to disposal of soils in a landfill (on site or off site) or treatment, and is also
required for some methods of soil washing or chemical fixation. Typically, excavation depths are limited
to the depth of the groundwater table. Since the depth to the water table at the site varies during the
year, scheduling of the excavation operations during the low water table season would be appropriate.
If groundwater is encountered, some method of dewatering may be necessary (subsection 3.2.7.1).
Temporary excavations will typically be performed with side slopes of I vertical to I horizontal (1:1) to
protect workers and equipment within the excavation in accordance with Occupational Safety and Health
Administration (OSHA) requirements. This technology is feasible for use at the M-1 Settling Basins.
3.2.5 Treatment
The contaminated soils and sludges at the M-1 Settling Basins can be treated to reduce their mobility,
toxicity, or volume. This treatment may be physical, chemical, biological, or a combination. This
treatment can be accomplished with or without source collection methods described in the previous
section. Treatment methods not requiring source collection are called in-situ methods and are described
in subsection 3.2.5.1. Onsite treatment methods are described in subsection 3.2.5.2. Offsite treatment
technologies are discussed in subsection 3.2.5.3.
3.2.5.1 In-situ Treatment TechnoloWies
Three technologies are identified as in-situ treatment measures:
0 In-situ vitrification3 In-situ chemical fixation
* In-situ soil washing
3.2.5.1.1 In-situ Vitrification. In-situ vitrification is a thermal treatment process that consolidates
contaminated soils into a hard, impermeable, stable glass and/or crystalline product. The process passes
an electric current among four electrodes placed in the ground in a square array. Heat from the electric
current melts the soil and rocks and pyrolyzes organic materials. During the process, metallic and other
inorganic materials are dissolved into or encapsulated in the vitrified mass.
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The system reaches up to 3600 F, well above the 2000 * F to 2500 * F fusion temperature of soils. Since
soil is not electrically conductive once the moisture has been driven off by initial heatup, a conductive
mixture of flaked graphite and glass frit is placed between the electrodes as a "starter path.* As the
graphite is consumed, the current is transferred to the molten soil, which becomes progressively more
conductive. When the electric current is cut off, the molten volume cools and solidifies. Because of the
intense chemical and structural changes, subsidence accompanies cooling, and some backfilling andregrading are required.
The process generates considerable gases from volatile constituents in the soil, by-product gases from
pyrolysis of larger organic molecules and volatile metals. The gases and by-products migrate to the
surface of the vitrified zone where they combust in the presence of oxygen. A gas collection hood and
offgas treatment system control gas emissions containing volatile metals and products of incomplete
Il combustion.
The process has been applied at both bench and field scale on electroplating wastes, dioxin waste,radioactively contaminated soils, and a waste pile of mixed containerized organic wastes. The typical
field-scale energy consumption ranges from 500 to 1,000 kW per 100 tons of waste. This technology may
be effective for the M-1 Settling Basins.
3.2.5.1.2 In-situ Chemical Fixation. Chemical fixation technology for either metal or organic
contaminants is potentially available without excavation of soils. At least one supplier has demonstrated
a pilot-scale system to drill and blend waste material in place with a fixative or bonding agent. The
process consists of drilling into the waste or soil with a boring rod with two liquid channels. While therod is being lifted, bonding agents supplied by grout pumps are injected through the channels and mixed,
eventually setting into a vertical cylindrical column of impermeable inorganic crystalline or cemented
material.
This technique is still in the experimental stage, and the test system has been designed for an organic
contaminated soil. No demonstration is available for metals that are present at the M-1 Settling Basins.
Therefore, this technology has not been selected for further evaluation.
3.2.5.1.3 In-situ Soil Washin . In-situ soil washing has been applied at the test or pilot level for both
organic and metal contaminated soils. The process consists of saturating the contaminated zones with
chelate, solvent, or diluent via injection wells, and collecting the introduced fluid and entrained
contaminant via a second series of wells, producing a washing circuit.
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Several potential problems may be encountered with this approach. First, the chelate or solvent, by
rendering the contaminants soluble, may spread the contamination if the collection system is not
completely effective. Second, because of the uncertainties of distribution patterns, large quantities of
solutions must be applied. Third, contact patterns and residence time are less certain than in an above-
ground system. For these reasons, in-situ soil washing is not retained for further consileration.
3.2.5.2 Onsite Soil and Sludge Treatment Methods
Three technologies are identified as onsite treatment measures for contaminated soil and sludge:
* Chemical fixation/stabilization
Soil washing/solution mining
* Vitrification
3.2.5.2.1 Chemical Fixation/Stabilization. Chemical fixation/stabilization refers to treatment methods
that surround or encapsulate waste components in a stable inorganic matrix. The treatment additives
are selected to:
* Minimize contaminant spread by agglomerating the wastes and reducing the transfer surface
area
• Reduce the solubility, toxicity, or mobility of hazardous components
3 Solidify or otherwise improve the handling or structural characteristics of the waste
Stabilization generally refers to those processes that add materials to change the pH, limit the solubility
or mobility, or otherwise chemically alter the environment around the contaminant molecule. This
process may solidify the waste or contaminated soil, or may leave it either friable or close to its original
consistency after treatment.
Chemical fixation involves applying additives of the type and quantity that will produce a monolithic
block of high structural integrity or a friable product. This process produces a stable inorganic polymer
lattice that includes the contaminants in the lattice.
Chemical fixation/stabilization can be accomplished by various means; most are referred to in terms of
the additives used to treat the waste. The two approaches discussed herein are the cement process,
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which is a chemical process, and the pozzolanic silicate process, which is a physical process. Both
processes will require a solids-handling operation consisting of the following basic steps:
I 1. Excavation of contaminated soils2. Temporary storage on a pad on site
3. Blending with additives in a high shear mixer or pug-type mill
4. Reaction time in a solidification cell3 5. Replacement into either the excavation pit or a landfill
3.2.5.2.2 Cement Process. The cement process is based on the addition of primarily portland cement
or other cementitious materials and water, which will mechanically incorporate waste components into
a rigid matrix when it cures. However, many wastes, especially organic contaminants remain leachable3from the cured cement since they are not chemically bound. This process elevates the bulk pH to a level
at which most metal ions are in the insoluble hydroxide or carbonate form. The actual cement matrix
3 is a calcium-silicate hydrate.
The metal salts are not stable over a wide pH range, and potentially, even precipitation is acidic enough
to initiate leaching. This process, when used alone, is generally not effective on some metal salts such
as salts of lead, copper, and zinc. Hence, the cement process is usually used in conjunction with other3 processes as a final hardening agent.
3.2.5.2.3 Pozzolanic Silicate Process. The pozzolanic process forms a matrix from fine ground siliceous
materials such as fly ash, blast furnace slag, or kiln dust with calcium oxide or gypsum and water.
Silicate content is often augmented by addition of solutions of sodium or potassium silicate. As with the
cement process, this process increases the weight and volume of the waste. However, depending on
additive ratios, the product consistency may remain clay-like to friable rather than a cemented solid.
This system has been applied to both divalent metal contaminants and organic contaminants in field-
scale remediations. This system is effective in binding heavy metals because they chemically react with
the silicate materials as the initiators of the gel or setting process. The presence of oil and grease may
interfere with the reaction, as do some sulfates, dichromates, and carbohydrates. Oil and grease are not
expected to be factors in the treatment at the M-I Settling Basins.
Both cement and pozzolanic processes utilize readily available materials and conventional mixing
equipment. Some combinations of chemical fixation or stabilization methods may be feasible for the
M-1 Settling Basins.
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3 3.2.5.2.4 Soil Washing/Sglution Mining. Soil washing, also referred to as solution mining whenperformed as a batch operation, consists of mixing contaminated soil with a chelating agent or solvent
to dissolve and remove the entrapped metals and organics. In the batch process, a tank or plastic-lined
pit is filled with excavated soils in a working pile or heap. The pile is sprayed and flooded with thetreatment solvent or chelate and the leachate collected and recycled. The solution is recycled until thecontailnant concentrations in both the soil and the treatment solution are in equilibrium, and no further
extraction from the soi will occur. The solution is then diverted and solids extracted via vacuumfiltration or other dewatering process. The remaining liquids are either processed for reuse orchemically or thermally destroyed. The filtrate sludge is suitable for recycling in a smelting furnace forrecovery of the metal constituents and thermal destruction of any organic content. The solution process
significantly reduces the volume of metal-bearing solids to a smaller amount more economically andsafely transported to an offsite recovery treatment/disposal facility.
I The batch process can be carried out completely on site except for any smelter recovery step. Thisprocess has been applied to ore piles in the precious and commercial metals industry and is referred to
as "heap leaching."
Soil washing can also be conducted as a continuous process by utilizing a froth flotation. In thisapplication, the soils are screened prior to the addition of cleansing agents and water to form a slurry.This slurry is routed to parallel flotation cells. Then the contaminated froth is drawn off the top, and
the slurry is pumped to wet-scouring tanks for a final water rinse. The cleaned slurry is then dewateredby filtration, leaving a soil that can be returned to the site or disposed of as clean fill. The
contamination is collected in the form of a concentrated sludge, which can be incinerated or landfilled.This process configuration is usually applied to organics-contaminated soil.
I This process has been conducted on a bench- and pilot-scale basis in Europe with excellent removal
efficiencies reported on soils with concentrations of contaminants in the range of those at the M-1
Settling Basins (Brochine, undated). This process can also be applicable for metals removal. However,the process configuration for metals removal is normally a countercurrent decantation process. This3 approach offers the possibility of addressing both metals and organics.
The waste material in the M-1 Settling Basins has been shown to have an alkaline pH. An excessiveamount of acid would be required to dissolve the calcium salt and reduce the pH before the metals
could be solubilized and washed from the soil, making soil washing an inefficient method of treating theM-1 Settling Basins waste. There is also the possibility that arsine gas may be formed during this
process. Therefore, this process will not be considered further.
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3.2.5.2.5 Vitrification. Vitrification is a thermal treatment technology used to transform the physical
and chemical characteristics of a hazardous solid waste so that the organic contaminants are destroyed,
and treated residues contain primarily inorganic hazardous material immobilized in a vitreous mass.
Vitrification can be applied in-situ, as described in subsectio .j 3.2.5.1.1, or above ground as described
herein. Inorganic contaminants should remain entrained in the glass melt, while any organic compounds
are oxidized at the reactor temperature of approximately 3000 * F.
The reaction chamber is divided into upper and lower refractory-lined sections. The upper section
accepts the waste feed via gravity and contains gases and other products of pyrolysis; the lower section
contains a two-layer molten zone for both the metallic and siliceous melts. The feed is gravity fed into
the reactor by conveyor. The offgas and particulates are drawn off by an induction fan to an offgas
treatment system. This system usually consists of a cyclone, baghouse, acid gas scrubber, and if
necessary, a carbon filter. Particulate and gas streams, as well as the carbon filter, can be recycled to
the reactor.
There are several vitrification processes -,urrently available; each has characteristic reaction conditions
(e.g. temperature, oxygen content) -ind solids-handling methods. One vitrification process is
commercially available in full-scale operation. However, this process has not been applied to volatile
metals, aad the vendor currently has no plans to modify the process to treat volatile metals. Therefore,3 this technology will not be retained for further evaluation.
3.2.5.3 Offsite Treatment
One technology, chemical fixation/stabilization, is identified as an offsite treatment measure.
3.2.5.3.1 Offshie Chemical Fixation/Stabilization. Chemical fixation/stabilization refers to a treatment
method that surrounds or encapsulates waste components in a stable inorganic matrix. To utilize this
option off site would involve the following basic steps:
3 1. Excavation of contaminated soils and sludges
2. Transportation to a treatment facility
3. Blending with additives in a high shear or pug-type mill
4. Reaction time in a solidification cell
5. Burial in an existing commercial RCRA-landftdl
This process uses readily available materials and equipment and is technically feasible.I3-11
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3.2.6 Temnorarv Storage/Disposal
Soil, concentrated sludges, and other solid wastes may require disposal before or after treatment. This
disposal -.an be either onsite temporary storage or offsite disposal at a properly permitteo facility. This
section evaluates technologies for the temorary storage/disposal of soils, sludges, and other -olid waste.
3.2.6.1 Onsite Temoorarv Storage
Two technologies have been identified for onsite temporary storage:
I Temporary waste pile
6 Solid waste landfill
3.2.6.1.1 Temporary Waste Pile. Solid wastes that have been classified as hazardous under 40 CFR
Part 261 would be stored in a temporary waste pile that substantially complies with the design
requirements of 40 CFR 264, Subparts L and N, requirements for such a facility. Design requirements
currently include double liners, leachate collection and treatment, capping, surface water control, and
a groundwater monitoring system. This technology is feasible for temporary storage.
3.2.6.1.2 Solid Waste Landfill. A selected soil/sludge treatment technology may be effective in
declassifying the material as hazardous as defined in 40 CFR Part 261. Therefore, hazardous waste
storage requirements would be unnecessary. Temporary storage of solid waste on site in a facility
designed to meet EPA's solid waste landfill requirements is feasible.
3.2.6.2 Offsite Disposal
Two alternative methods are available for offsite disposal of soils/sludges:
• Disposal in a hazardous waste landfill
* Disposal in a solid waste landfill
3.2.6.2.1 Disrosal in a Hazardous Waste Landfill. Contaminated soils and sludges or treated solid waste
streams from treatment processes can be disposed of off site in a commercial hazardous waste landfill.
The nearest, fully permitted hazardous waste facility to RMA is the USPCI Grassy Mountain landfill
near Clive, Utah. Offsite disposal will require excavation and management ,f groundwater through
one or more of the treatment technologies described in subsection 3.2.7. This is a feasible technology
for the M-1 Settling Basins.
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3.2.6.2.2 Disposal in a Nonhazardous Solid Waste Landfill. Nonhazardous solid wastes from soil/sludgetreatment processes can be disposed of in a nonhazardous waste landfill. Several of these exist in the5 area. Disposal at a facility with less stringent controls than a hazardous waste landfill will require thatthe waste transported off site be delisted and considered nonhazardous. Since there will be somep nonhazardous debris generated in these operations, this will be considered 3 feasible tcrhnology.
3.2.7 Dewatering and Water TreatmentIThe objective of this IRA is to mitigate the threat of release from the M-1 Settling Basins. Groundwaterremediation is beyond the scope of the IRA. Therefore, water treatment will only be conducted if
implementation of the selected alternative requires dewatering operations. It has been assumed that thechosen IRA alternative can be implemented during the dry season, which would make dewatering andwater treatment unnecessary. If this is impossible, the following dewatering and water treatment
alternatives will be considered.
13.2.7.1 Dewatering Process
Contaminated soils/sludges can be dewatered by using one or more of the following processes:
• Pumping from wellsI Pumping from collection trenches excavated below the water table* Excavation and filtration
3.2.7.1.1 Groundwater Well Pumping. Groundwater pumping techniques involve the active manipulation
and management of groundwater to contain or remove a plume or to adjust groundwater levels to
prevent the formation of a plume. At the M-1 Settling Basins, the objective is to lower the contam-
inated groundwater table a sufficient depth to allow for effective soil remediation. This soil remediation
method may be in-situ or may require excavation. In either case, the presence of groundwater may limitthe effectiveness of the chosen methods. Types of wells used in the management of contaminated
groundwater include wellpoints, suction wells, ejector wells, and deep wells. The selection depends ongroundwater depth as well as the hydrologic and geologic characteristics of the aquifer.
U This method of groundwater control is a technically feasible method of dewatering the soil beneath the
M-1 Settling Basins.
32.7.1.2 S. Subsurface drains are usually any type of buried conduit used to conveyp and collect aqueous discharges by gravity flow. They create a zone of influence much like an extraction
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well. Drains have distinct advantages over wells for use in shallow aquifers, such as at the M-1 Settling
Basins. Pumping on a shallow well field in strata of low or variable hydraulic conductivity can be
problematic if a continuous hydraulic boundary is necessary. Also, operation and maintenance costs are
generally lower for drains with respect to wells.
The main components of a drainage system are a drain pipe for conveying flow to a wet well, a gravel
pack around the drain pipe, a filter to prevent dogging (if fines are a problem), backfill, and a manhole
or wet well for groundwater collection and pumping.
This method of groundwater control is a technically feasible, potentially cost-effective method of
dewatering the soil beneath the M-1 Settling Basins.
3.2.7.1.3 Filtration. Soils and sludges can be dewatered after excavation by using a couple of techniques.
Soils can be allowed to drain within a bermed area after excavation. The drained water is collected in
a low-point sump for subsequent water treatment. This is effective for removing only a fraction of the
associated groundwater but may be applicable for processes requiring water, for example, chemical
fixation/stabilization.
If the excavated solids require a greater level of dewatering for subsequent processing, this can be
accomplished by using equipment such as a vacuum filter. This filtration operation can be run in a batch
or continuous mode. In a continuous mode, the soil/sludge is fed through a hopper and a rotating drum
equipped with a cloth filter medium. A vacuum is drawn on the interior of the drum that pulls waterthrough the cloth media. The dried soil/sludge is then separated from the cloth medium either by astationary knife or by gravity.
This type of filtration can typically produce a dried sludge with water content as low as 10 percent. This
technology is feasible for alternatives that require significant dewatering prior to solids processing.
3.2.7.2 Water Treatment Processes
Historical information and data from the spring 1989 investigation indicate that groundwater in the
vicinity of the M-1 Settling Basins contains many of the organic and inorganic compounds detected in
the South Plants area. Predominant classes of groundwater contaminants include arsenic, mercury,
organochlorine pesticides, volatile organic compounds, and semivolatile organic compounds. Whether
or not the M-1 Settling Basins contribute to this aquifer degradation does not affect the conclusion that
this water, once extracted, will require treatment prior to either reinjection or disposal. The following
alternatives for water treatment will be discussed in this section.
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1• Carbon adsorption0 Rotating biological contactor* Fixed-bed bioreactor* Powdered activated carbon/activated sludge• Ultraviolet-enhanced chemical oxidation* Chemical precipation/flocculation
0 Ion exchange
i Activated alumina
3.2.7.2.1 Carbon Adsorption. Granular activated carbon (GAC) adsorption is commonly used forremoval of organics from water. The removal efficiency depends on factors such as the polarity,
solubility, and size of the molecules to be removed. The adsorption occurs in packed columns with flow
rates and contact times determined by properties of the contaminants to be removed.
The carbon must be regenerated when saturated or when the effluent reaches unacceptable levels of
contaminants. At these times, the bed of carbon is removed from the packed column and replaced with
new material. The saturated carbon is thermally treated in a regeneration furnace for destruction of
adsorbed organic compounds and reused. Poor adsorbability or higher contaminant concentrationsresult in frequent regenerations.
S The volatile halogenated organics present in the alluvial aquifer in the vicinity of the M-1 Settling Basins
(see Section 2.0) are among the least sorbable species with reference to GAC. These compounds canI be effectively removed from groundwater streams if present in dilute concentrations. However, the cost-
effectiveness of adsorbing high concentrations of volatile halogenated compounds from groundwater is3 limited because breakthrough of the carbon beds would occur by one or more species long before the
carbon is saturated. This would result in frequent carbon changeout producing large volumes of waste3 solids for regeneration or disposal. For this reason, GAC will not be considered further.
3.2.7.2.2 Rotating Biological Contactors. Rotating biological contactors (RBC) are considered for5 groundwater treatment because of their relatively low energy use and simple operation. An RBC system
consists of a series of disks covered with a film of active biomass that is partially submerged in the
wastewater. Disk rotation alternately exposes the attached biomass to the substrate-rich wastewater and
to the atmosphere. Substrate (including hazardous constituents), measured as soluble biochemical
oxygen demand or chemical oxygen demand (BODs or COD), is oxidized and converted to a new5 biomass, soluble metabolic by-products, and gaseous end products. Sequential groups of disks, called
stages, are designed to meet specific effluent requirements based upon soluble BOD removal in each
* stage.
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3l Important controlling factors of the RBC system are influent substrate concentration, surface hydraulic
load, disk rotational speed, effective disk surface area, submerged disk depth, liquid retention time,
wastewater treatment temperature, and number of stages. Therefore, the prediction of achievable
effluent concentrations from an RBC wastewater treatment system is difficult because of the number
of the process operating parameters.
Studies indicate the RBC process for municipal wastewater is approximately first order with respect to
BOD concentration; that is, the rate of bio-oxidAtion is proportional to the amount of oxidizable organic
matter remaining. The design of the standard municipal RBC process is primarily based on the
hydraulic loading rate (gal/day/ft) and the organic loading (lbs BOD/day/ft2). Temperature can affectperformance of the fixed-fdm process, as it influences substrate removal rates, oxygen saturation values(also mass transfer driving forces), and the diffusivities of oxygen and substrate. At wastewater
temperatures of 13 * C (55 F), changes in hydraulic or organic loading have been shown to result insignificant changes in BOD removal.
The staging of RBC units is a major design element. The simulation of plug flow operation by proper
staging results in a higher treatment efficiency. RBC facilities are typically designed with four or more
stages operating in series depending on the substrate removal desired.
£ General advantages of an RBC system:
• Simple operation and maintenancei High resistance to shock and hydraulic loading
* Successful operation with or without air supply"* Low sludge production with good sludge settleability and dewaterability
• Low power consumption"* Low heat loss
Major disadvantages of an RBC system:
0 It does not address the arsenic in the groundwater (arsenic may be toxic to biomass) and is
inefficient in removing chlorinated hydrocarbons
* The technology is relatively unproven for the conditions at RMA
0 Engineering costs are higher because of the process development studies required (i.e., pilot
studies)
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Since an RBC does not significantly reduce the arsenic concentration in the water, it would have to be
used in conjunction with another treatment step design to reduce arsenic concentrations to acceptable
discharge levels. Because this technology will require feasibility testing, it will not be retained for further
consideration for this IRA.
3.2.7.2.3 Fixed-Bed Bioreactor. Conventional, flow-through aeration basins (lagoons and tanks) are of
limited effectiveness in biodegradation of low coacentration influent waters. The primary limitation
consists of the inability of microorganisms to find sufficient organic substrate to feed upon in a high-
volume, low-concentration system, i.e., insufficient contact between biomass and contaminants.
Fixed-bed bioreactors are adaptations of aerobic bioreactors that allow the processing of diluted
wastewaters. A fixed-bed reactor consists of one or more tanks or vessels fitted with a high surface area
plastic or other fill material, which is baffled or compartmentalized to reduce throughput velocity and
maximize retention time. Microorganisms are seeded at a startup with nutrients and carbohydrate
solution to encourage initiation of a biomass growth on the fill material surface. Feedwater undergoes
intimate contact with the fill surfaces over a long enough time period to allow microbes to locate and
degrade contaminant molecules. Aeration is augmented by bottom spargers or diffusers.
Fixed-bed systems are available in modular portable tank systems with built-in aerators and fill media,
allowing relatively simple mobilization/demobilization. These systems have been effective at several
large-scale groundwater remediation sites. This technology is feasible as part of an overall groundwater
treatment system, though other steps will be required for arsenic removal.
3.2.7.2.4 Powdered Activated Carbon/Activated Slud"e. Powdered activated carbon (PAC) addition
to a conventional activated sludge wastewater treatment system can significantly improve the
performance of the system because removal of recalcitrant organic compounds is improved. Biological
treatment of municipal and industrial wastewater is a well-proven technology. However, process
performance can be detrimentally affected by low organic loading and the presence of refractory
compounds that may pass through the system. Addition of a powdered carbon can improve perfor-
mance by adsorbing these components and providing a longer residence time for biological metabolism.
In a biologically active, powdered activated carbon treatment (PACT) system, powdered carbon is added
to a conventional activated sludge system. The powdered carbon adsorbs organic contaminants that have
not been degraded biologically and is removed from the wastewater in a clarifier. The clarifier
underflow is recycled back to the contactor tank, with a small side stream removed for disposal. The
spent carbon sludge must be disposed of at an EPA-permitted disposal facility. The spent carbon may
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also be regenerated on site using a wet air oxidation process; however, for intermediate water
throughput rates (500 to 1,000 gpm), offsite disposal of the spent carbon sludge is more economical.
PACT installations are successfully being used for the treatment of municipal, industrial, and mixed
municipal/industrial wastes (Zimpro, Inc. 1987). Incineration and/or landfdling of the sludge is
employed at a number of these installations.
Ability to vary the PAC dosage gives flexibility to the process. At RMA, the dose could vary with the
flow rate or concentration to provide control over effluent quality. This would enable adjustment of
treatment to achieve necessary removal levels.
The advantages of this treatment method are:
"• Fast rate of adsorption
"* Easy-to-control removal efficiency
* Lower carbon requirement than GAC
Disadvantages of this treatment technology are:
• High capital costs
* Problems with the handling of spent carbon sludge
• Does not remove arsenic
In general, the treatment efficiency of a PACT system approximates that of other biological treatment
processes. However, the PACT approach generates a considerably larger quantity of secondary waste,
i.e., sludge, to achieve comparable treatment results. Based on the availability of equivalent treatment
technologies generating less waste, PACT will not be evaluated further.
3.2.7.2.5 Ultraviolet(UVM-enhanced Chemical Oxidation. In theory, organic matter in a wastewater
stream can be completely destroyed by chemical or thermal oxidation. The by-products of complete
oxidation of a hydrocarbon are water and carbon dioxide. Thus, it should be theoretically possible to
convert even the most toxic hydrocarbons to innocuous chemicals that would not have adverse
environmental effects.
There are many methods of oxidizing organic chemicals. Thermal methods are the most familiar, but
they are unsuitable for diluted, high-volume liquid waste streams because of the large energy
requirements for vaporizing the bulk liquid. Therefore, for most diluted liquid streams, some method
3-18(11111C02.3100) (11/18/89)
wooard-C ye Conwuwaats
of chemical oxidation is preferred to remove the objectionable components from the wastewater. The
most suitable chemical oxidation processes identified for this study were UV-enhanced oxidation by
ozone or hydrogen peroxide. These processes have been shown to achieve complete destruction of
target organics when operated under optimal conditions.
Ozone is a powerful oxidizing agent that has traditionally been used in wastewater treatment systems
as a disinfectant and viricide. Ozone is produced when a high voltage is imposed across a discharge gap
in the presence of a gas containing oxygen. Because ozone is a relatively unstable gas, it must be
generated on site from air or pure oxygen. In a pure oxygen system, offgases from the ozone contact
chamber can be recycled back to the ozone generator for more efficient oxygen use. In an air system,
offgases are usually vented to the atmosphere. Ozone quickly reverts to oxygen in the environment and
does not pose a significant environmental impact when used in an air-fed system.
UV fight has been shown to markedly increase the rate of oxidation in ozonation reactors treating
wastewaters. This is attributed to the higher energy of the UV light excitation of the organic molecules.
Unfortunately, the use of UV light enhances only the rate of oxidation but not the efficiency. Thus, the
quantity of ozone required will not be reduced appreciably by UV radiation.
Hydrogen peroxide, when exposed to UV lig•i!, readily reacts to form hydroxyl radicals. These radicals
are also strong oxidants that can similarly react with organic contaminants in water. The choice of
optimal oxidant and operating conditions can only be determined after a bench-scale test. The selection
of an oxidant (ozone or hydrogen peroxide) is addressed later in the selection process. An additional
post-treatment step would be required for the metals contamination in the water because UV-enhanced
chemical oxidation does not remove metals. This technology is feasible for the destruction of organics
in groundwater.
3.2.7.2.6 Chemical Precioitation/Flocculation. Chemical precipitation/flocculation involves adding
agents to remove the contaminants from solution, followed by sedimentation or other physical separation
to remove the resulting insoluble particles from the water. Chemicals added to remove contaminants
from solution perform either of the following:
* Increase or decrease the system pH to a level where the contaminant is less soluble
* React with the contaminant to form an insoluble salt
* Shift the solubility equilibrium of the contaminant to make the existing compound insoluble
3-19(11111C02-3100) (11/18/89)
Woodward-Clde Cosuftants
Additionally, polymer flocculants are frequently added to help agglomerate the resulting suspended
particles into "floc" or larger particles that can be more easily removed by sedimentation, filtration,
centrifugation, or other mechanical means.
Removal of particulates is generally accomplished by long-residence time sedimentation (settling) in a
clarifier. The combination of microfiltration and recycling of the concentrate through the reagent mix
portion of the system until large settleable particle size develops is also applied to metal salt systems.
Both approaches often require subsequent dewatering operations for reduction of the generated sludges.
Dewatering is commonly performed by pressure fdtration using either a belt-filter press or a plate-and-
frame filter. The final sludge cake (approximately 30 to 50 percent solids) would be landfilled with or
without chemical fixation/stabilization. This technology is technically feasible for metals removal.
3.2.7.2.7 Ion Exchange. Ion exchange treatment removes selected ions from water by electrochemically
collecting them on a polymeric surface containing sites of opposite charge. Systems suited to water
treatment generally contain one or more pressure vessels (exchangers) filled with "resin beds" consisting
of beads of various polymer resins containing either cationic or anionic sites. When the water or
aqueous waste has passed through the beds long enough to saturate the sites, flow is stopped and the
beds "regenerated" by contacting with a regenerate solution (acids, caustic, or other solutions as
appropriate) to remove the contaminant ions. The spent regenerate is either processed for reuse,
concentrated for recovery of the contaminants, or processed for disposal.
Ion exchange is a potentially feasible technology for the removal of arsenic.
3.2.7.2.8 Activated Alumina. Arsenic can be adsorbed from a water stream on the surface of activated
alumina. Activated alumina is essentially a highly porous form of aluminum oxide. Aluminas are
available both as granules and as fine powders; hence, they provide a large surface area and adsorptive
capacity per unit volume (Considine 1974). This technology is technically feasible and is currently in use
with GAC for arsenic removal in the Building 1727 sump treatment system located in Building 1713 at
RMA (ESE 1988).
3.2.7.3 Treated Water Disposal
There are two onsite methods of disposal for treated water: reinjection through wells and reinjection
through percolation beds or trenches. Discharge to a storm drain is the only available offsite disposal
option.
3-20(11111C02-3100) (11/18/89)
I Woodwsd. yde Constat
1 3.2.7.3.1 Reiniection through Wells. The conventional method of injecting fluids or reinjecting extracted
water into an aquifer is the use of injection wells screened at strategic depths. However, that injection
water will probably be laden with suspended and microbial solids unless it has first been filtered.
Filtering can add considerably to total water treatment costs. If the injected water is not filtered,
injection well screens are likely to clog readily with solids and will not be dependable for long-term
service. In addition, screens provide surface area for microbial growth and may plug, even with fluids
that have been filtered of solids and microbes. For these reasons, this technology will not be considered
further.
3.2.7.3.2 Reiniection through Percolation Beds or Trenches. Discharge water can be pumped or
drained over a bed of crushed rock or gravel in order to enhance its percolation through the vadose
zone. The percolation bed is a simple technology that is more reliable than injection wells, since it is
less susceptible to fouling resulting from microbial growth.
3.2.7.3.3 Discharge to Storm Drain. Treated water can be routed to the nearest storm drain which is
equivalent to surface water discharge. Surface water discharge at RMA ultimately outfalls to the south
fork of the Platte River.
Surface water discharge of treated effluent water would require that the effluent concentrations meet
the National Pollution Discharge Elimination System (NPDES) outfall limits of the RMA.
3.3 SUMMARY OF RETAINED TECHNOLOGIES
Tables 3-3 and 3-4 summarize the available technologies. Several identified technologies were evaluated
as not being applicable based on technical implementability. The remaining technologies are used to
formulate the alternative remediation scenarios of Section 4.0.
II
3-21j (11111C02-3100) (11/18/89)
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4.0DEVEIOPMENT AND EVALUATION OF ALTERNATIVES
This section evaluates interim response alternatives that have been developed for the M-1 Settling
Basins. The alternatives are designed from one or more feasible technologies introduced in Section 3.0.
The alternatives address both the contamination on site and any waste streams generated as part of
treatment. These aternatives me then evaluated with respect to:
* Overall protectiveness of human health and the environment
* Compliance with Applicable or Relevant and Appropriate Requirements (ARARs)
* Reduction in mobility, toxicity, or volume
* Short- and long-term effectiveness
* Implementability
Costs associated with the alternatives will be addressed in Section 5.0.
4.1 INTERIM ACTION ALTERNATIVES
Eight alternatives have been developed as interim response actions (IRAs) according to Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by SARA,
1986, guidance (Environmental Protection Agency 1988). The suite of alternatives includes
administrative, containment, treatment, and temporary storage/disposal options. The alternatives are:
1 No action
2 Monitoring
3 Institutional controls
4 Slurry wall with cap
5 Multilayered cap
6 In-situ vitrification
7 Chemical fixation with onsite storage8 Chemical fixation with offsite disposal
The first three alternatives do not involve containment or treatment but are included per EPA guidance
document, "Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCIA,"
Interim Final October 1988.
4-1-- (11111Co2-3100) (11/19/89)
I
The next two alternatives represent in-place containment with no treatment. These are considered
appropriate since this is an IRA. The contamination would remain in place until such time as the
overall site remediaticn addressed this area.
The next two alternatives represent feasible onsite treatment scenarios. One is an in-situ alternative not
requiring excavation, while the other requires excavation and soil/sludge treatment on site.
The final alternative consists of excavation and onsite soil/sludge treatment with final disposal at a fully
permitted commercial hazardous waste landfill
Each alternative is described in the following subsections. These designs are conceptual in nature. The
details of the selected alternative will be determined during final design.
4.1.1 Alternative I - No Action
This alternative assumes that no action will be taken to contain or treat contaminated soils and sludge
at the M-1 Settling Basins. Additional groundwater monitoring would not be required if this alternative
is selected.
4.1.2 Alternative 2 - Monitorin2
This alternative assumes that the only action taken at the M-1 Settling Basins is additional groundwater
monitoring. This monitoring would track the continuing effect, if any, of the M-1 Settling Basins on
the alluvial aquifer. In addition, monitoring will be part of Alternatives 3 through 8.
The monitoring consists of quarterly sampling and analysis of groundwater from existing monitoring Well
Nos. 01083, 01524, 01503, 01504, and 36193. The water will be analyzed for the following analytes:
* Volatile halogenated organics
I * Volatile aromatic organics
* Semivolatile halogenated organics
• Total and dissolved arsenic
* Total and dissolved murcury
* ICP metals
* pH
4-2(11111CO02-3100) (11/19/ll9)
SWoodwardy.c consutans
This information will be included as part of the comprehensive monitoring program at the Rocky
Mountain Arsenal (RMA). Analysis of these data will help to evaluate how much the M-1 Settling
Basins are actively degrading groundwater quality in the area and will provide information necessary to
develop a final response action.
Groundwater sampling will occur on a quarterly basis for this alternative and alternatives 3 through 8.
In addition to groundwater monitoring, an air monitoring program will be designed. The program will
monitor ambient ai for figitive dust and organic volatilization. It is assumed that four monitoring
stations will be set up on all sides of the site.
The sampling effort will include:
"* Dust PM 10, for metals and fugitive particulates
"* PUF (polyurethane foam), for pesticides
0 Tenax/activated carbon, for volatile organic compounds
Air sampling will be performed during the construction operations period of Alternatives 4 i.rough 8.
4.1.3 Alternative 3 - Institutional Controls
The institutional control alternative consists of constructing a fence around the site. This would entail
the construction of approximately 910 lineal feet of chainlink fence with controlled access points (i.e.,
locked gates).
4.1.4 Alternative 4 - Slurry Wall with Cat
The slurry wall and cap alternative would consist of constructing a slurry wall around the M-1 iettling
Basins and a cap covering the area enclosed by the slurry wall. This alternative would enclose the
source of contamination and reduce the migration of hazardous constituents. The slurry wall and cap
would be designed to contain the contamination source until a final remedy action is selected and
implemented.
4-3(1111IC02-3100) (11/19/89)
Woodward-.Cyde Consultants
4.1.4.1 Construction of 360 " Slur Wall
The slurry wall would enclose the three M-1 Settling Basins, as well as the berms surrounding the basins,
and provide lateral containment of the contamination source. The enclosed area would be about
300 feet long and 115 feet wide. The size of the enclosed area would be slightly less thav one acre. The
slurry wall would be about 910 feet long and would penetrate through the upper silty, sandy material3 into the underlying Denver Formation (approximately 18 feet). For this feasibility study, it is assumed
conservatively that the slurry wall would be keyed at a depth of 5 feet into the confining layer. Any
excess spoil remaining after slurry wall construction will be placed under the cap.
4.1.4.2 Construction of a Multilayered CaDUThe cap would be designed and constructed to cover the entire area enclosed by the slurry wall (about
one acre). The cap would consist of, from the base upwards, an 18-inch thick compacted clayey soil
layer, a 60-mil-thick high-density polyethylene (HDPE) flexible membrane liner, a synthetic drainage
net, a geotextile filter fabric, and a 1-foot protective soil layer. The cap would be sloped from the center5I to the edge at about 2 or 3 percent to facilitate surface water runoff from the cap. This cover design
would reduce infiltration of surface water into the M-1 Settling Basins. Water infiltrating the cover
would collect onto the clayey soil/flexible membrane composite layer and would be drained to the
outside of the cap by gravity through the synthetic drainage net. The geotextile filter fabric would
reduce the risk of the synthetic drainage net being clogged by soil particles from the overlying soil layer.
Treatment of the protective soil layer, such as cement or asphalt addition, may reduce erosion potential
and maintenance of the cover.
I 4.1.5 Alternative 5 - Multilayered Cao
This alternative would consist of covering the M-1 Settling Basins with a cap to reduce infiltration of
surface water. The extent and design of the cap would be the same as that for the slurry wall and cap
alternative described above. The cap would be designed and constructed to cover the M-1 Settling
Basins, about one acre.
i 4.1.6 Alternative 6 - In-situ Vitrification
5 Contaminated soils and sludge would be vitrified in-situ by introducing sufficient electrical current
through the soil to raise the soil temperature to its melting point. The current would be introduced by
four electrodes placed in the ground in a square array. A slurry wall will be constructed around the in-
situ vitrification (ISV) area. It is assumed that dewatering is unnecessary. The water within the
(1111C02-3100) (11/19/39) 4-4
I
Woodward. Comuft
boundaries of the slurry wall will be vaporized during the ISV and water from the surrounding region
will not migrate through the slurry wall. The sequence of activities that would be performed in this
alternative consists of the following:
* Construction of a 360" slurry wall
* In-situ vitrification in stages throughout the 1-acre site
Regrade the site
4.1.6.1 Construction of a 360 * Slurry Wall
The slurry wall would be constructed as described in subsection 4.1.4 with the exception that the depth
of the slurry wall will only be approximately 15 feet. In this case, the slurry wall is used to provide a
temporary barrier to groundwater recharge in the vitrification area.
4.1.6.2 In-situ Vitrification
The vitrification process is initiated by the placement of four electrodes in a square array approximately
18 feet apart to a depth of approximately 7 feet. An offgas collection hood will be installed that will
route offgases and steam under negative pressure to the offgas control system housed on site in a
trailer. A second trailer will house the electrical switchgear that will condition the 4160-volt power
obtained from the site power distribution system and deliver it to the electrodes.
The offgas control system will cool, scrub, and filter the vapors collected from the offgassing melt.
Assuming this process drives off the 47 percent water fraction of the sludge, approximately
700,000 gallons of water in the form of steam, with trace contaminants of arsenic and mercury, will be
generated. This will be condensed indirectly by using a circulating glycol system. Noncondensed acid
gases will be absorbed in a packed scrubber column. As a final step in the air pollution control
sequence, the exhaust gases will pass through an activated carbon absorber prior to venting to the
atmosphere.
The condensate will have elevated concentrations of arsenic and mercury, as well as an alkaline pH.
This will require pH adjustment and precipitation of arsenic and mercury to reduce arsenic and mercury
levels to accepted discharge limits. Mercury may be in a recoverable form. Actual wastewater treatment
will be determined during pilot testing. Any sludge generated in the wastewater treatment will be added
to unvitrified soil/sludge for subsequent vitrification. The treated effluent water will be discharged to
the alluvial aquifer through a percolation bed.
4-5(1111C02.-3100) (11/19/39)
aI
Woowa. Consultants
The process will vitrify the soil/sludge at a rate of approximately 3 to 5 tons/hour. Once the melt is
complete, the system will be dismantled and moved to the neit area of the vitrification sequence, leaving
the melt to cool. To process the approximately 9,000 yoP of soil, the operation will take about 5 months.
4.1.63 SiLWaig
After the vitrification process is complete, some subsidence will have occurred, approximately 40 to 50
percent of the depth of melting. Imported fill will be brought in from nearby, by using standard earth-
moving equipment (e.g., loader, end dump trucks, etc.) as necessary to ensure positive surface drainage
away from the vitrified area.
4.1.7 Alternative 7 - Chemical Fixation with Onsite Storane
This alternative would include excavation of approximately 10,800 yd 3 (9,000 yd3 plus a 20 perceni
bulking factor) of sludge and soils by sections or subareas to be treated, mixing of the excavated
contaminated soils with one or more fixation agents, testing of the treated portions to ensure treatment
effectiveness, and placement of the treated soil in an onsite temporary waste pile. This sequence would
be repeated for successive subareas until the entire area to be chemically fixed is treated. Two general
types of mixing methods are commonly used for the chemical fixation process: batch mixing on the
surface of a workpad, or semicontinuous mixing in cement handling equipment, such as a pug mill. The
semicontinuous approach is more likely to be employed for this remediation.
Chemical fixation is based on treatment methods that surround or encapsulate waste components in a
stable inorganic matrix. The treatment additives are selected to accomplish one or more of the following
results: reduce the mobility of contaminants by reducing the surface area exposed to leaching fluids,
reduce the solubility or toxicity by chemically binding the contaminants into a crystal or inorganic lattice,
or solidify or otherwise improve the handling properties of the bulk waste.
3 Typical additive& are sodium silicate, portland cement, fly ash, or kiln dust. The resulting material will
remain friable even after curing;, that is, it will not harden into a concrete mass. The exact composition
and volume of fixing agents are not currently known, since these treatment specifics vary somewhat with
the vendor, and the vendor has not yet been selected. For the same reason, an exact increase in volume
is not known, although it is estimated that bulking factors of between 10 and 20 percent by volume could
be expected. A bench-scale treatability test program should be conducted to determine the proper
additives and additive ratios.
I4-6I (11111C02-3100) (11/19/39)
Woodward. yde ConslAtants
Chemical fixation is well-suited for the metals contamination at this site. Certain organic contaminants
Sin the surface soil can also be immobilized by chemical fixation.
A storage pad will be constructed for storage of excavated soils prior to chemical fixation. The storagepad will have a clay liner and sump for drainage to minimize contact between cozsuminated and
uncontaminated soil and precipitation. A second pad of similar size will be constructed nearby for3 storage of treated soils. The pads will be constructed with low permeability liners. Each pad will be
surrounded on the perimeter with a containment berm. Contaminated soils will be run through screens
to separate large fragments. The screening device will most probably be a slanted vibrating screen or
series of screens with a screen size of 1/4 inch. Larger fragments may be crushed prior to fixation. Any
uncrushable debris will be collected and cleaned or transported to a hazardous waste disposal facility.
After screening and crushing, the soil will be moved into and through the fixation machinery and then
to the fixed materials pad. The area required for the equipment would be approximately 2,000 ft. For
the purpose of cost and schedule development, it is assumed that excavation and treatment of the
contaminated soils will proceed in 500 yd3 per day increments using two units. Soil excavation at theM-1 Settling Basins may require backhoes, loaders, bulldozers, and personal protective equipment.
During operations, confirmation samples from the treated soil stockpile and the excavation limits wiHl
be collected for chemical testing, for comparison to leachate and/or cleanup criteria. The fixation
contractor will take performance samples of the treated material after mixing and will test for chemical
stability. In addition, one sample of every 10 will be tested with the proposed EPA toxicity characteristic
leaching procedure (TCLP) test to indicate leachable organic and metal materials.
3 The chemically fixed soils and sludges will be temporarily stored in an onsite waste pile. This waste pile
would be constructed with a clay liner and cap as well as a synthetic liner, leachate monitoring and
Sollection sump, and groundwater monitoring wells. The fixed soils/sludges must pass leachability tests
before they are stored in the waste pile.
4.1.7.1 Temtorary Waste Pile
I A waste pile would be constructed above ground in the vicinity of the M-1 Settling Basins for the
temporary storage of the chemically fixed materials. The waste pile would be designed to hold about
11,900 yd' (9,000 yd3 plus 20 percent for excavation bulking, plus 10 percent for bulking from the fixation
process) of contaminated materials. The bottom liner and leachate collection system would consist of,
from the base upwards, an 18-inch-thick compacted clayey soil layer, a 60-mrl-thick HDPE flexible
membrane liner, a synthetic drainage net, and a geotextile filter fabric. The bottom liner would be
(21111Co2-3100) (11/19/89) 4-7
I4-U
SWoodwaCydeCom~bnb
sloped at a minimum of 2 percent toward a leachate collection sump. Liquids collecting in the leachate
collection sump would be removed. The treated soils would be placed in the waste pile in lts and
compacted to minimize settlement after placement. The first lift of soil in the waste pile would be
placed in a manner that would not damage the completed liner system. The total height of the soil in
the waste pile would be about 15 feet. Once all the contaminated materials have been placed in the
waste pile, a cover would be constructed to close the waste pile. The cover system would consist of,
[rom the base upwards, an 18-inch-thick compacted clayey soil layer, a 60-mil-thick HDPE flexible
membrane liner, a synthetic drainage net, a geotextile filter fabric and a 1-foot-thick protective soil layer.
Treatment of the protective soil layer, such as cement or asphalt addition, may be used to improve the
erosion resistance of the soil and reduce maintenance.
4.1.7.2 Transportation to Temnorarv Waste Pile
The fixed soil/sludge will be placed on dump trucks and sent to the nearby waste pile described in the
previous section. Assuming a chemical fixation rate of 500 yd' per day, this operation should take
approximately 17 days and involve approximately 30 to 35 daily round trips of a 15 yd' capacity dump
truck between the M-1 Settling Basins and the newly constructed waste pile.
4.1.7.3 Site Restoration
After completion of the excavation operation, the site will be regraded. The site will then be revegetated
for erosion control.
Site operations for the chemical fixation process with onsite storage are as follows:
Excavate contaminated soil, dewater if necessary, and transport to storage pad.
Collect confirmation samples from base of final excavation.
Screen all debris and solids 1/4-inch or greater in diameter from the soils.
* Crush oversizA d material to the appropriate size.
Collect untreatable debris, if present, and store temporarily or haul to a hazardous waste
landIll.
• Convey contaminated soils from the storage pad to the fixation processing equipment.
4-8(11111C02.3100) (11/19/89)
WoodadC'd Conmman
* Add fixation chemicals and water to the soils and mix to uniformity.
0 Transfer the fixed soil to the treatment pad for temporary storage and sampling.
£ Backfill the basin area with engineered fill.
* Construct waste plde.
1 Transport fixed soil to the onsite temporary waste pile.
4.1.8 Alternative 8 - Chemical Fixation with Offsite DistOnW
Contaminated soils and sludges can be excavated and disposed of offsite in a hazardous waste landfill.Due to the high water content of the M-1 Settling Basin sludges, this material would need to be
chemically fixed before it can be placed in a landfill. The sequence of activities that would be performed
in this alternative consists of the following:
* Chemical fixation of soil/sludgeI * Transportation to offsite landfill
* Site regrading
4.1.8.1 Chemical Fixation of Soil/Sludge
Soil and sludge from the M-1 Settling Basins would be chemically fixed according to the same
procedures described in subsection 4.1.7.
4.1.8.2 Transportation to Offsite Landfill
The dump trucks hauling contaminated soil/sludge will be decontaminated and secured prior to hauling.
The soil will be sent to the USPCI hazardous waste landfill near Clive, Utah. Hauling costs per yard
of material are cited in Section 5.0. Therefore, the total volume of 11,900 yd3 was used for the cost
calculations. Disposal was quoted per ton, so a density of 1.5 tons/yd3 was used to convert volume to
Sweight.
4-9I (~1111Co2.310o) (11/19/sg)
Wooodward-ty COminstmms
4.1.83 Site RegradLng
After excavation, the site will be regraded and revegetated as described in subsection 4.1.73.
42 INTERIM AMriON EVALUATION (RnEA
The interim action alternatives just presented will be evaluated based on the following criteria:
* Overali protection of human health and the environment
* Conformance with ARARs
- Reduction of moblity, tosicity, or volume
I * Short- and long-term effectiveness
* Implementability
3* Cost
The IRA objectives identified in paragraphs 22.5 through 22.7 of the Federal Facility Agreement are
included in these criteria. The definition and interpretation of these criteria are outlined in this section.
Costs are discussed in Section 5.0.
How each alternative addresses each of the evaluation criteria will be presented in greater detail in
Seciton 6.0; however, a summary of alternative evaluation criteria is presented in matrix form in
Tables 4-1 and 4-2. (Tables are located at the end of this section.)
4.2.1 Overall Protection of Human Health and the Environment
This criterion assesses whether each alternative provides adequate protection of human health and theenvironment. Assessment of protection draws upon other evaluation criteria, especially short-term
effectiveness and compliance with ARARs and considers whether each alternative poses unacceptable
short-term or cross-media impacts.
4.2.2 Conformance with ARAR
One criterion used to evaluate each of the interim action alternatives is compliance with ARARs.
Alternatives that meet all ARARs will be preferred because they ensure that interim action will be
conducted in a manner that protects human health and the environment.
4-10o(1111Co2-3100) (11/19/99)
I Woodward-eld Consulants
4.2.3 Reduction of Mobility. Toxicity, or Volume
Reduction of waste mobility, toxicity, or volume reduces the potential of that waste to harm humans
or the environment. This evaluation criterion evaluates the process effectiveness to reduce organic andmetals concentrations and to reduce waste quantity. Some of the specific issues addressed in the evalua-
tion of this criterion include the following:
S• Does the process completely destroy organics?
* Does the proces permanently immobilize organics?
* Does the process reduce the mobility of organics?
* Does the process permanently immobilize the metals?
* Does the process reduce the mobility of metals?
* Does the process significantly reduce the toxicity of organics?
* Does the treatment produce a reduction in hazardous waste volume?
* Does the process result in an increase in hazardous waste volume?
4.2.4 Short- and Long-term Effectiveness
The effectiveness of the interim alternatives will be considered in terms of its short- and long-term
effectiveness in meeting the remedial action objectives.
Short-term effectiveness examines the effectiveness of alternatives in protecting human health and the
environment during the construction and implementation period until objectives have been met. Short-
term effectiveness has two elements: community protection and worker protection.
Community protection considers any risk that results from implementation of the proposed interim
action. Some of the questions that identify potential community risks from a remedial process are:
I * If a process failed, what would be the effect on the community?.
* Are effective mitigation measures available to reduce community risk if the process fails?
• How will the effects on the community be addressed and mitigated?
Worker protection evaluations during interim response activities consider the potential threats that may
be posed to workers and the effectiveness and reliability of protective measures that could be taken.
Some considerations for worker protection issues are:
(1nInICo2-3100) (11/19/89) 4-11
WoowKkd-C
* What are the risks to workers that must be addressed?
* How will the risks to workers be addressed and mitigated?
* What risks remain to the workers that cannot be readily controlled?
Long-term effectiveness examines the effectiveness of each alternative in maintaininZ protection of
human health and the environment after response objectives have been met. This evaluation is divided
with two main criteria: magnitude of residual risk and adequacy and reliability of long-term controls
to manage that residual risk. Some of the questions addressed in this evaluation are:
I• What risk remains, relative to a no-action alternative?
3 What type of long-term monitoring is required?
What difficulties and uncertainties may be associated with long-term operation and
maintenance?
3 Is there a clear and significant long-term benefit in implementing this alternative now?
34.2.5 Imjmentabiiii
The implementability criterion addresses the technical and administrative feasibility of an alternative and
the availability of various services and materials required for its implementation. Some of the specific
issues to be evaluated include the following questions:
1 Is the technology generally available and sufficiently demonstrated on a full scale?
U * What difficulties or uncertainties are related to implementation; could these lead to schedule
delays?
* Are the necessary equipment and specialists available?
S WVll more than one vendor be available to provide a competitive bid?
3 Are adequate treatment, storage capacity, and disposal services available; can additional
capacty/scrvAces be developed if ncessary?
3 What are the monitoring requirements during implementation?
4-12I (IIII1COZ-3100) (11/19/39)
I Woodwa ed- Cokmmmants
I What effect would this alernative have on implementing a final remedy?
0 How long would i take to implement the alternam ?
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5.0ECONOMIC EVALUATION OF ALTERNATIVES
IThe alternatives developed in Section 4.0 have been evaluated with respect to the threshold criteria of
protectiveness of human health and the environment, and compliance with applicable or relevant andappropriate requirements (ARARs). They have also been evaluated with respect to:
U0 Reduction of mobility, toxicity, or volume0 Short- and long-term effectiveness5* Implementability
This section discusses the costs involved with implementing each alternative. Since the Federal FacilityAereement states that the Interim Response Action (IRA) Decision Document should select the mostcost-effective alternative that meets the objective of this IRA, these estimated costs will be afundamental tool in the decision-making process.
5.1 ECONOMIC ASSUMPrTIONS
The cost estimates developed for the evaluated alternatives are intended to be used as comparativetools. These study estimates can be considered to have an accuracy of +50 to -30 percent. These
estimates are divided into capital costs and operating and maintenance (O&M) costs. A present worth5 analysis is also presented to compare alternatives with different expenditure patterns.
Whenever possible, vendor quotes for capital and O&M costs are used. However, several other sources
of costs have been utilized. These include generic unit costs, previous similar estimates (modificd bysite-specific information), and conventional cost estimating guides. All costs that are obtained from5 these materials will be escalated to third quarter 1989 by using the Chemical Engineering plant cost
index.
I The following engineering assumptions have been used:
i For the purpose of cost comparisons, a 5-year operating life has been assumed for the IRA.
This assumption may be altered by the final Record of Decision (ROD).
I
* 5-1
(IIIIIC1o2-3100) (11t/18/89)
1*.'oodwardClyd. Consultants
I Connections to electricity, natural gas, water, and sewer will be provided by RMA at
no additional cost to the project.
i Offsite disposal of hazardous solids will be at the USPCI Grassy Mountain landfill
near Clive, Utah. Bulk waste will be shipped off site in trucks.
* An operating rate of 7,000 hours/year will be used for continuous processes utilizing
mechanical equipment. This allows for approximately 20 percent downtime for
maintenance and repair.
0 Engineering, design, construction management, and startup are assumed to be 20 to
50 percent of major purchased equipment (MPE) costs to $5,000,000; 15 to 20 percent
of MPE for equipment costs in the range of $5,000,000 to $10,000,000; and 5 to
10 percent of MPE for equipment costs in excess of $10,000,000.
I A contingency of 20 percent has been applied to all capital and O&M cost estimates.
0 Utility costs have been estimated by using the following rates:
Electricity* $0.085/kwhWater S3.76/1,000 gallonsNatural gas S3.359/1,000 ft3
Sewer $1.50/1,000 gallons
In-situ vitrification was costed at $0.05/kwh because major user rates may be lower.
• Offsite disposal costs have been estimated by using the following rates:
Transportation $120/tonDisposal $140/ton
0 O&M costs incurred after the first year have been discounted at 5 percent.
0 Treatment operations conducted by a turn-key vendor are considered under O&M
costs, regardless of treatment duration.
I
5-2(11I ICo2-3100) (11/18/89)
I
Woodwardc yde Consutant
5.2 ALTERNATIVE (X)STING
5.2.1 Alternative I - No Action
This alternative assumes that no action will be taken to contain or treat contaminated soi/sludge at
the M-1 Settling Basins. This alternative results in no capital or O&M costs; therefore, present worth
costs are not included in Table 5-1. (Tables 5-1 through 5-9 are located at the end of this section.)
5.2.2 Alternative 2 - Monitoring
Costing for the monitoring alternative includes groundwater monitoring. For the groundwater
monitoring plan, it is intended to only have an operations and maintenance cost. Capital costs have not
been included because only existing monitoring wells are to be sampled.
Air monitoring is specific to ambient air and will include monitoring stations in each direction from the
M-1 Settling Basin area.
Air monitoring would be performed only during the construction operations period of Altrnatives 4
through 8. For details on air monitoring capital and O&M costs, refer to Table 5-2.
5.2.2.1 Capital
No capital cost is associated with groundwater monitoring because it is assumed that only existing
monitoring wells will be sampled.
Direct cost for the air monitoring program will include the necessary monitoring equipment and
program design. Including the 20 percent contingency, the capital cost for air monitoring is $62,400.
This capital cost will be included in the total for Alternatives 4 through 8.
5.2.2.2 Operations and Maintenance
Groundwater and air monitoring O&M costs include quarterly sampling, analysis, and reporting. The
totals for groundwater and air monitoring O&M costs are $168,000 and $174,700, respectively.
Groundwater monitoring O&M costs are included for Alternatives 2 through & Air monitoring O&M
costs are included during the construction operations of Alternatives 4 through 8.
5-3(1111IC02.3100) (11/19/39)
3 Woodward-Clyde Consultants
b 5.2.2.3 Present Worth Value
The iotal present worth value for the monitoring alternative of $727,000 is the present worth value for
the groundwater monitoring O&M cost of $168,000 over 5 years.
5.2.3 Alternative 3 - Institutional Controls
Cost details for Alternative 3 are presented in Table 5-3. The total capital required for this alternative
is $34,900. Besides the 20 percent contingency, the only major cost items are fencing, at $9,100 and site
prcparation, at $20,000.
I 5.2.3.1 Operations and Maintenance
U No additional operations and maintenance costs have been assumed for Alternative 3. Only the O&M
*" cost for groundwater monitoring is included at $168,000.
5.2.3.2 present Worth Value
I The total present worth value for Alternative 3 is $762,000, which is a total of the capital and the present
worth value of the O&M cost over 5 years.
5.2.4 Alternative 4 - Slurry Wall with Cap
Cost details for Alternative 4 are presented in Table 5-4 and the capital, O&M, and present worth value
are summarized in Table 5-1.
5.2.4.1 Capital Cost
Some of the major cost items for the slurry wall and cap construction are: slurry wall and cap
construction, $273,600 and $84,300, respectively, and engineering design and supervision, $94,100.
Including the 20 percent contingency, the total capital requirement is $677,300. Construction activities
are assumed to be completed in 1 year.
5.2.4.2 Operations and Maintenance
In the summary table, the groundwater and air monitoring O&M costs from Table 5-2 of $342,700 has
bcen included for the construction operations period (year 1). During the post-interim action period,
54(1 I 1C02-3100) (11/18/89)
L
Woodw Clyde Coatuftas
the cost items are groundwater monitoring at S168,000 and cap maintenance at $25,000 for a total
closure period O&M cost of $193,000.
5.2.43 Present Worth Value
The present worth value for this alternative is $1,655,000, which is the total of the capital and the
present worth value of the operations and post interim action O&M costs.
5.2.5 Alternative 5 - Multilayered Can
Cost details are presented in Table 5-5 and the present worth value summary is presented in Table 5-1.
5.2.5.1 Capital Cs
Major cost items for the total capital requirement are as follows: cap construction, $84,300; site
preparation, $50,000; air monitoring capital, $62,400; and engineering and supervision, $39,300. The
total capital requirement for this alternative is $283,300, including a 20 percent contingency. The
construction period is anticipated to be within 1 year.
5.25.2 Oerations and Maintenance Cost
Similar to Alternative 4, the operation period cost is $342,700, and the post-interim action O&M cost
is $193,000.
5.2.53 Present Worth Value
The total present worth value for this alternative is $1,261,000, which is a total of the capital and the
present worth value of the two O&M costs over the 5-year period.
5.2.6 Alternative 6 - In-situ Vitrification
Cost details for this alternative are presented in Table 5-6 and summarized in the present worth value
Table 5-1.
5-5
(11111Co023100) (11/19/39)
Woodward.dctl.Conuants5.2.6.1 Capital Costs
The total capital requirement of $470,600 is based on the slurry wall construction, and engineering andsupervision. Upon completion of the slurry wall, the in-situ vitrification (ISV) process is to begin and
is expected to last less than 1 year (assuming one ISV unit at the site).
5.2.6.2 Onerations and Maintenance
Annual O&M costs for in-situ vitrification is based on $20 per ton for offgas treatment operations andI $400 per ton for electrical charges. Because of the increased power requirement, a lower charge of$0.05 per kwh was used instead of $0.085 per kwh.
Total ISV cost is $8,000,200 for the operations and maintenance. This includes the ISV operation,operations monitoring, and engineering and supervision. The operations period costs occur during year
1. From years 2 to 5, post-interim action monitoring costs of $168,000 occur, which include ground-water monitoring and reporting.
5.2.6.3 Present Worth Value
The present worth value for the operations and post-interim action period O&M cost is $8,657,000.
5.2.7 Alternative 7 - Chemical Fixation with Onsite Storage
Cost details for this alternative are presented in Table 5-7, and a present worth summarization is
presented in Table 5-1.
5.2.7.1 Capital Cost
The total capital requirement is S624,100, whi,-h is based on the liner construction, air monitoring
capital, site preparation costs, and onsite waste pile construction. The liner will contain excavated soilsprior to treatment as well as treated soil until testing for the chemical fixation is complete.
5.2.7.2 Annual Operations and Maintenance
The total annual O&M cost of $1,708,100 includes the chemical fixation process at $65 yd3, soilshandling, sampling, and monitoring. The chemical fixation will be completed within 1 year and is to
(I11IIC02-3100) (11/18/89) 5w6
Woodward-ctyde Consftants
occur at a rate of 500 yd3 per day (assuming one unit). Performance sampling is based on one sample
per 500 yd3 of soil.
A post-interim action cost of $193,000 will occur from years 2 to 5 and will include both air and
groundwater monitoring as well as cap maintenance on the onsite waste pile.
5.2.7.3 Present Worth Value
The total present worth value is $2,902,000, which is a total of the capital, the present worth for the
operating period (year 1), and the post-interim action period (years 2 through 5).
5.2.8 Alternative 8- Chemical Fixation with Offsite Disposal
Cost details for this alternative are presented in Table 5-8.
5.2.8.1 Capital Cost
The total capital requirement of $161,900 is based on air monitoring capital and site preparation, which
includes removing the existing structures on the basins, as well as engineering and supervision.
5.2.8.2 Operations and Maintenance
Operations and maintenance costs consist of a first year operations cost of $8,378,400, and a post-
interim action O&M of $168,000 which will occur during years 2 through 5. First year O&M costs
include the chemical fixation process at $65/yd', performance sampling and monitoring, transporting
17,800 tons to the USPCI hazardous waste facility in Utah, and engineering and supervision. The
chemical fixation will be completed at a rate of 500 yd3 per day (assuming one unit). Performancc
sampling is based on one sample per 500 yd' of soil/sludge. Disposal and transportation costs are based
on $140/ton and $120/ton, respectively.
5.2.8.3 Present Worth Value
A total present worth value of $8,708,000 is the sum of the capital cost and an operations and post-
intcrim action O&M present worth cost of $8,546,000.
5-7I (II111CO2-3100) (11/18/89)
1Woodwar.aClyde Consultant
5.3 SENSITIVrrY ANALYSIS
A sensitivity analysis has been performed to determine which alternative will be affected by changesin the design basis presented in Section 2.5. Table 5-9 summarizes this analysis and presents the total
prcs.'n worth value for each alternative per sensitivity parameter. A discussion of each parameterfollows.I
6 Additional Volume of Contaminated Soil: The volume of soil/sludge to be treated wasI increased by assuming a larger extent of contamination. An extended boundary was added"to the known boundaries of the M-1 Settling Basins, making the dimensions of the basins140 feet by 330 feet, and the contamination was assumed to extend to 10 feet below groundsurface. The containment alternatives (Alternatives 4 and 5) were only affected slightly by
this change with their total present worth value increasing 3 to 5 percent. Chemical fixation
with onsite storage total present worth costs were increased 48 percent. In-situ vitrificationand chemical fixation with offsite disposal were most affected by the volume change with total
present worth cost increases of 73 percent and 78 percent, respectively.
* Double Unit Treatment Costs: Costs for three of the alternatives are dependent on the unittreatment costs. The unit treatment costs were doubled to evaluate the effect of the unit costs
on the total cost for the alternatives. Doubling the unit treatment costs had an effect similar
to adding additional volumes of contaminated soil. Total present worth costs for chemicalfixation with onsite storage increased 37 percent. Total present worth costs for ISV increased
dramatically: 81 percent. Total present-worth costs for chemical fixation with offsite disposalonly increased 11 percent because the bulk of the cost for that alternative is because of the
transport and disposal of the fixed material.
5-8(11 1ICO2-3100) (11/18/89)
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TABLE 5-2 clydeALTERNATIVE 2-GROUNDWATER AND AIR MONITORING: COST ESTIMATE
M-1 SETTLING BASINS
ASSUMPTIONS:
(I) Groundwater samples at $5000/sample (includes labor, health and safety at Level B personal protectiveequipment, and analytical)
(2) Quarterly groundwater sampling of 5 wells (20 samples/year)(3) Quarterly groundwater monitoring will continue for the duration of the IRA(4) For air monitoring, assume quarterly sampling of four stations on each side of the site(5) Air monitoring samples include dust/metals, pesticides, and volatile organics
UNITITEM DESCRIPTION UNIT COST AMOUNT COST(A) GROUNDWATER MONITORING:
CAPITAL COSTS (NONE)ANNUAL OPERATIONS AND MAINTENANCE(1) Sampling of Existing Monitoring Wells Ca. $5,000 20 $100,000
(2) Reporting/ Data Interpretation ea. $10,000 4 $40,000
Subtotal S140,000(3) Contingency at 20% 28,000
ANNUAL O&M COST $168,000(B) AIR MONITORING:
(for construction operations only
Alternatives 4 through 8)
CAPITAL COST(I) DUST PM I0 a. $3,000 4 $12,000(2) PUF ca. $4,000 4 $16,000(3) Sampling Pumps ca. $1,000 4 $4,000(4) Technical Support and Program Design ea. $20,000 1 $20,000
Subtotal $52,000(5) Contingency at 20% $10,400
TOTAL CAPITAL COST $62,400
ANNUAL OPERATIONS AND MAINTENANCE (O&M)(I) DUST / metals sampling Ca. $1,000 16 $16,000
(2) PUF 0a. $300 16 $4,800(3) Volatiles a. $300 16 $4,800
(4) Labor ea. $20,000 4 $80,000(5) Interpretation & Reporting a. $10,000 4 $40,000
Subtotal $145,600(6) Contingency at 20% 29,120
ANNUAL O&M COSTS $174,720
5-10
Wo diwa,-v Coame
TABLE 5-3ALTERNATIVE 3 - INSTITUTIONAL CONTROLS: COST ESTIMATE
M-1 SETTLING BASINS
ASSUMPTIONS:
I (I) Institutional controls costs include groundwater monitoring
(2) Institutional controls consist of perimeter fencing (910 ft), which assumes a10 foot boundary around the contaminated area
UNITITEM DESCRIPTION UNIT COST AMOUNT COST
CAPITAL COST
(1) Site Preparation $20,000(2) Fencing L.F. $10 910 $9,100
Subtotal $29,100
(3) Contingency at 20% $5,820
TOTAL CAPITAL COST $34,920
ANNUAL OPERATIONS AND MAINTENANCE (years 1-5)
(1) Grounawater Monitoring (Item A, Table 5-2) $168,000
ANNUAL O&M COSTS
5-11
TABLE 5-4 Clyde ConsultALTERNATIVE 4 - SLURRY WALL WITH CAP: COST ESTIMATE
M-1 SETTLING BASINS
ASSUMPTIONS:
(1) Site preparation will consist of grading and filling of low-lying areas to control runoff(2) A slurry wall will surround the three M- 1 Settling Basins. The length of the slurry wall is ;stimated
to be 910 feet. The depth is assumed to be 25 ft.(3) The multilayered cap design is based on most appropriate protection for an interim action(4) Monitoring costs are detailed in Table 5-2
UNITITEM DESCRIPTION UNIT COST AMOUNT COST
CAPITAL COST
(1) Air Monitoring Capital (Item B, Table 5-2) $62,400(2) Site Preparation (includes removal $50,000
of above-ground equipment)(3) Slurry Wall ft2 $12 22,800 $273,600
(4) Construct cap:Clay yd3 $8 2,400 $19,200Flexible membrane yd2 $5 4,800 $25,920Synthetic drainage net yd2 $3 4,800 $15,840Geotextile yd2 $2 4,800 $10,560Protective soil layer yd3 $8 1,600 $12,800
Cap Cost $84,320
Subtotal $470,320(5) Engineering and Supervision at 20% $94,064
Subtotal $564,384(6) Contingency at 20% $112,877
TOTAL CAPITAL COSTS $677,261
ANNUAL OPERATIONS AND MAINTENANCE COSTS
A. Construction Operations Monitoring (year 1) $342,720(Items A and B, Table 5-2)
B. Post-Interim Action Monitoring (years 2-5)
(1) Groundwater Monitoring (Item A, Table 5-2) $168,000(2) Cap Maintenance $25,000
ANNUAL POST-INTERIM ACTION O&M COSTS $193,000
5-12
Woodard-Cwyde CQmwiants
TABLE 5-5ALTERNATIVE 5 - MULTILAYERED CAP: COST ESTIMATE
M-1 SETTLING BASINS
ASSUMPTIONS:
(1) Site preparation will consist of grading and filling of low-lying areas to control runoff.(2) Cap design is the same as the slurry wall and cap alternative.(3) Monitoring costs are detailed in Table 5-2.
UNITITEM DESCRIPTION UNIT COST AMOUNT COST
CAPITAL COST
(I) Air Monitoring Capital (Item B, Table 5-2) $62,400(2) Site Preparation (includes removal of above-ground equipment) $50,000
(3) Construct Cap:
Clay yd3 $8 2,400 $19,200
Flexible Membrane yd2 $5 4,800 $25,920Synthetic Drainage Net yd2 $3 4,800 $15,840Geotextile yd2 $2 4,800 $10,560Protective Soil Layer yd3 $8 1,600 $12,800
Cap Cost $84,320
Subtotal $196,720(4) Engineering and Supervision at 20% $39,344
Subtotal $236,064(5) Contingency at 20% $47,213
TOTAL CAPITAL COST $283,277
ANNUAL OPERATIONS AND MAINTENANCE COST
A. Construction Operations Monitoring (year 1)(Items A and B, Table 5-2) $342,720
B. Post-Interim Action Monitoring (years 2-5)
(1) Groundwater Monitoring (Item A, Table 5-2) $168,000
(2) Cap Maintenance $25,000
ANNUAL POST-INTERIM ACTION O&M COSTS $193,000
5-13
hWoodward.C| de Consutants
TABLE 5-6
ALTERNATIVE 6 - IN-SITU VITRIFICATION: COST ESTIMATEM-1 SETTLING BASINS
I ASSUMPTIONS:
* (I) Slurry wall constructed to 15 ft to reduce potential groundwater recharge in the vitrification area(2) There will be no dewatering within the slurry wall(3) Vitrification cost includes $400/ton for electricity and $20/ton for offgas treatment. Assume treatment rate of
6 tons/hr (144 tons per day) for a project life of 105 days (assume I year)(4) Soil volume - 9,000 yd3 at 1.35 tor/yd3
UNITITEM DESCRIPTION UNIT COST AMOUNT COST
CAPITAL COST
(1) Air Monitoring Capital (Item B, Table 5-2) $62,400(2) Site Preparation (includes removal $50,000
Sof above-ground equipment)(3) Slurry Wall ft2 $12 13,700 $164,400
(4) Site Restoration $50,000Includes: Backfill, grading and replanting
Subtotal $326,800
(5) Engineering and Supervision at 20% $65,360Subtotal $392,160
(6) Contingency at 20% $78,432
TOTAL CAPITAL COST $470,592
SIANNUAL OPERATIONS AND MAINTENANCE (year 1)
(1) Construction Operations Monitoring $342,720(Items A and B, Table 5-2)
(2) Mobilization/Demobilization $110,000(3) Vitrify Solids
soil vitrification ton $400 12,150 $4,860,000
offgas treatment ton $20 12,150 $243,000
SVitrification $5,555,720
(4) Engineering and Supervision at 20% $1,111,144Subtotal $6,666,864
(5) Contingency at 20% $1,333,373
ANNUAL O&M COSTS $8,000,237
ANNUAL POST-INTERIM ACTION O&M COSTS (years 2-5)
Groundwater Monitoring (Item A, Table 5-2) $168,000
5-14
Woodward.ctyde Consuftants
TABLE 5-7ALTERNATIVE 7 - CHEMICAL F..XATION WITH ONSITE STORAGE: COST ESTIMATE
M-1 SETTLING BASINS
E ASSUMPTIONS:
I (1) Onsite above-ground waste pile construction and filling operations will be performed within one year(2) Waste pile bottom liner system includes leachate collection system(3) Waste pile cover consists of a multilayered systemI (4) Waste pile volume assumes a 20% bulking factor from excavation plus 10% buling from chemical fixation
(5) Soils will be excavated and stored on a temporary pad that will also contain the chemical fixing processequipment
I (6) Treatment will be conducted by a turnkey contractor within the first year
UNITI TEM DESCRIPTION UNIT COST AMOUNT COST
CAPITAL COST
I (1) Air Monitoring Capital (Item B, Table 5-2) $62,400(2) Site Preparation (includes removal of above-ground equipment) $50,000
I (3) Construct Waste PileWaste Pile Construction
Area Preparation yd3 $3 2,500 $7,500Clayey Soil Liner yd3 $8 2,500 $20,000Flexible Membrane Liner yd2 $5 4,900 $26,460Synthetic Drainage Net yd2 $3 4,900 $15,6S0Geotextile Filter Fabric yd2 $2 4,900 $10,780
Cover ConstructionClayey Soil Liner yd3 $8 2,600 $20,800Flexible Membrane Liner yd2 $5 5,200 $28,080Synthetic Drainage Net yd2 $3 5,200 $16,640Geotextile Filter Fabric yd2 $2 5,200 $11,440Protective Soil Layer yd3 $8 1,700 $13,600
Waste Pile Costs $170,980
(4) Liner Construction (for temporary storage and treatment facility) $100,000(5) Site Restoration $50,000
Subtotal $433,380(6) Engineering and Supervision at 20% $86,676
Subtotal $520,056* (7) Contingency at 20% $104,011
TOTAL CAPITAL COST $624,067
5-15
Woodwad.:ClVd Comultanft
TABLE 5-7 (Continued)
U ANNUAL OPERATIONS AND MAINTENANCE (year 1,
(1) Construction Operations Monitoring (Items A and B, Table 5-2) $342,720(2) Soils Handling (backfilling included) yd3 $12 10,800 $129,600(3) Chemically Fix Soils yd3 $65 10,800 $702,000(4) Performance Sampling and Monitoring yd3 $500 24 $11,880
I Subtotal $1,186,200
I (5) Engineering and Supervision at 20% $237,240
Subtotal $1,423,440
I (6) Contingency at 20% $284,688
ANNUAL O&M COSTS $1,708,128
ANNUAL POST-INTERIM ACTION O&M COST (years 2-5)I (1) Groundwater Monitoring (Item A, Table 5-2) $168,000
(2) Cap Maintenance $25,000
ANNUAL POST-INTERIM ACTION O&M COSTS $193,000
IIIIIIII
5-16I
Woodward.Clyde Conmutants
TABLE 5-8ALTERNATIVE B - CHEMICAL FIXATION WITH OFFSITE DISPOSAL: COST ESTIMATEp M-1 SETTLING BASINS
I ASSUMPTIONS:
(1) Soils will be excavated, and stored on a temporary pad that will also contain the chemical fixing process
equipment
(2) Treatment will be conducted by a turnkey contractor within the first year(3) Soils will be transported to the USPCI facility in Grassy Mountain, Utah at a cost of $120/ton
transportation and $140/ton disposal
(4) Soil amount = 6,400 yd3 + 20% excavation bulking + 10% chemical fixation bulking; assume 1.5 tons/yd3 for
fixed materialsUNIT
ITEM DESCRI'MTION I-NIT COST AMOUNT COST
I CAPITAL COST1) Air Monitoring Capital (Item B, Table 5-2) $62,400
2) Site Preparation (includes removal of $50,000
above-ground equipment)Subtotal $112,400
3) Engineering a:d Supervision at 20%
$22,480
Subtotal $134,880I 4) Contingency at 20% $26,976
TOTAL CAPITAL COST $161,856
' ANNUAL OPERATIONS AND MAINTENANCE (year 1)
(1) Construction Operations Monitoring $342,720
(Items A and B, Table 5-2)(2) Soils Handling (backfilling included) yd3 $12 10,800 $129,600
(3) Chemically Fix Soils yd3 $65 10,800 $702,000
(4) Performance Sampling and Monitoring yd3 $500 22 $10,800
(5) Transport to Offsite Facility ton $120 17,820 $2,138,400
(6) Offsite Landfill Disposal Fee ton $140 17,820 $2,494,800
Subtotal $5,818,320(7) Engineering and Supervision at 20% $1,163,664
Subtotal $6,981,984
(8) Contingency at 20% $1,396,397
ANNUAL O&M COSTS $8,378,381
ANNUAL POST-INTERIM ACTION O&M COSTS (years 2-5)
Groundwater Monitoring (Item A, Table 5-2) $168,000
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I WodwardclydeConsutants!* 6.0
CONCLUSIONS
This alternative assessment document has summarized the history and extent of contamination at the
IM-1 Settling Basins. This information was used to develop a basis by which technologies wereformulated into eight alternatives to address the contaminated soil and sludge at the site.
U• This section initiates the decision process by ranking the alternatives and classifying them as preferred,
marginally preferred, or not preferred. Preferred and marginally preferred alternatives are thenevaluated further based on the evaluation criteria described in Section 4.2.
6.1 ALTERNATIVE SCREENING
The eight alternatives were ranked using the decision logic shown in Figure 6-1. The alternatives have
bccn classified as one of the following:
* Preferred: Preferred alternatives meet the threshold criteria listed in Table 4-1 and
meet most of the evaluation criteria listed in Table 4-2 Preferred alternatives will be
considered further.
Marginally preferred: Marginally preferred alternatives meet the threshold criteria
listed in Table 4-1 to some degree and meet some of the evaluation criteria listed inIITable 4-2. Marginally preferred alternatives will be considered further.
Not preferred: Alternatives that are not preferred either do not meet the threshold
criteria of Table 4-1 or meet few of the evaluation criteria of Table 4-2. These3 alternatives will not be considered further.
3 The eight alternatives are classified in Table 6-1. There are two preferred alternatives:
* Alternative 6 - In-situ vitrification
• Alternative 7 - Chemical fixation with onsite storage
U6-1
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ALTERNATIVE
I*ALTERNATIVE MEET NO ALTERNATIVE IS NOT
II
I)I ~THRESHOLD CRITERIA: OVRPRROETO O UA EFERRE
3 DOESALTERNATIVE MEET MOST NO ALTERNATIVE IS
EVALUATION CRITERIA MARGINALLY PREFERRED3?
OYES
5 .ALTERNATIVE IS PREFERRED
THRESHOLD CRITERIA: OVERALL PROTECTION OF HUMAN HEALTHAND THE ENVIRONMENT
COMPLIANCE WITH ARARS
EVALUATION CRITERIA: REDUCTION OF TOXICITY, MOBILITY AND VOLUME* SHORT-TERM EFFECTIVENESS
LONG-TERM EFFECTIVENESSIMPLEMENTABILITY
COSTIJo No. : 22238Prepaedb ___KA.S Figure 6-1 IRA ALTERNATIVE
Prepred y K..S.RANKING3Date: 914/89O
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I TABLE 6-1ALTERNATIVE CLASSIFICATION
3 Alternative Classification Comments
1 1. No Action Not Preferred Not protective; no reduction i nmobility, toxicity, and vwlumne noshort- or long-termeffectiveness
2. Monitoring Not Preferred Not protective; no reduction inmobility, toxicity, and volume; no3 long-term effectiveness
3. Institutional Not Preferred Not protective; no reduction inControls mobility, toxicity, and volume; no
long-term effectiveness
4. Slurry Wall Marginally Preferred Somewhat protective;with Cap reduces mobility, does not reduce
contaminant toxicity or volume;good short-term effectivenew poorlong-term effectiveness
5. Multilayered Marginally Preferred Marginally protective; partiallyCap reduces mobility, does not reduce
contaminant toxicity and volume;good short-term effeinerss poorlong-term effectiveness
6. In-situ Vitrification Preferred Protective; reduces mobility,toxicity, and volume; good short-and long-term effectiveness; highcost
7. Chemical Fixation Preferred Protective; reduces mobilitywith Onsite Storage and toxicity, increases volume;
goo kiag-trnu effectiveness someshort-term effects possible;treatability testing required
8. Chemical Fixation Marginally Preferred Protective; reduces mobility andwith Offsite Disposal toxicity, increases volume; good
long-term effectiveness, butpotential short-term effectspossible; treatability testingrequired; high cost
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i These alternatives are protective of human health and environment and can be designed to meet
n ARARs.
There are three marginally preferred alternatives:
U Alternative 4 - Slurry wall with cap
* Alternative 5 - Multilayered cap
* Alternative 8 - Chemical fixation with offsite disposal
Alternatives 4 and 5 are somewhat to moderately protective of human health and the environment.
Alternative 8 is considered marginally preferred rather than preferred because it is extremely expensive
* for an !RA.
There are three alternatives that are not preferred:
* Alternative 1 - No action
n Alternative 2- Monitoring
* Alternative 3 - Institutional controls
U Alternatives 1, 2, and 3 are not protective of human health and the environment and will not be
considered further.
U The preferred and marginally preferred alternatives will be evaluated and screened in greater detail in
the following section.
6.2 ALTERNATIVE EVALUATION
Alternatives have been evaluated against the following criteria:
I * Reduction of contaminant mobility, toxicity, or volume
• Short-term effectiveness, including community protection and worker protection3) * Long-term effectiveness
* Implemeatability
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Woodward. yd. Consultants
Tables 6-2 through 6-7 (located at the end of this section) provide details of the evaluation. All
alternatives can be implemented in less than 1 year. A summary of the evaluation for each alternative
follows.
6.2.1 Alternative 4 - Slur Wall with Can
This alternative reduces the vertical and horizontal migration of contaminants, although the toxicity
and volume of contaminants are not reduced.
This alternative has good short-term effectiveness. Short-term effectiveness is evaluated based on the3 effect of the alternative on the community as well as workers at the site during implementation. Impacts
on the community during implementation are minimal. Risk to workers during construction can beft addressed by using common personal protection and site safety-hazard prevention techniques.
Long-term effectiveness of this alternative is somewhat limited because the alternative is based on a
containment technology. Containment does reduce the effects of the source of groundwater
contamination, but it does not actually remediate the source. The effectiveness of this alternative as5 a source mitigation measure would need to be re-evaluated periodically.
This alternative is based on demonstrated technology which can be easily implemented by a number
of contractors, although above-ground structures and underground utilities would need to be relocated.
3 6.2.2 Alternative 5 - Multilavered Can
This alternative reduces the vertical migration of contaminants, although the horizontal migration,
toxicity, and volume of contaminants are not reduced.
3This alternative has good short-term effectiveness. Short-term effectiveness is evaluated based on the
effect of the alternative on the community as well as workers at the site during implementation. Impacts
on the community during implementation are minimal. Risk to workers during construction can be
addressed by using common personal protection and site safety-hazard prevention techniques.
l3 Long-term effectiveness of this alternative is considerably limited because the alternative is based on a
partial containment technology. Containment does partially reduce the effects of the source of
6-53 (11112C02-3100) (11/18/89)
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groundwater contamination, but it does no., actually remediate the source. The effectiveness of thisalternative as a source mitigation '.•,ure would need to be re-evaluated periodically.
This alternative is based oca demonstrated technology that can be easily implemented by a number of
contractors, although above-ground structures would need to be relocated.
6.2.3 Alternative 6 - In-situ Vitrification
U This alternative destroys the organic contaminants, thereby reducing the toxicity of the material, and
also, either permanently immobilizes or recovers the metals. The process also reduces waste volume.
This alternative has good short-term effectiveness. Short-term effectiveness is evaluated based on theeffect of the alternative on the community as well as workers at the site during implementation. Impactson the community during implementation are minimal. Possible air emission impacts can be controlled
through redundancy of the system design. Risks to workers during implementation can be addressedby using common personal protection and site safety-hazard prevention techniques.
In-situ vitrification has good long-term effectiveness. Risk is substantially reduced by the destruction
of the organics and the immobilization or recovery of the metals.
This process has been effectively demonstrated on an engineering scale by the vendor. One concern
during the implementation would be that any above-ground structures and underground utilities would
need to be relocated.
6.2.4 Alternative 7 - Chemical Fixation with Onsite Storage
This alternative permanently immobilizes the contaminants, although the toxicity is not reduced andthe volume of the material is increased.
This alternative has fairly good short-term effectiveness. The only community impact may be airemissions generated during excavation and fixation; however, these can be controlled by shutting downthe operation if ambient air and wind monitoring indicate a possible threat. Any risks to workers duringimplementation can be addressed by using common personal protecion and site safety-hazard prevention
techniques.
6-6(11111co2-3100) (11/18/89)
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The long-term effectiveness of this alternative is good because the contaminants are permanently
immobilized. However, the onsite waste pile would require long-term monitoring and inspection, andj_ relocation of the fixed materials may be necessary depending on future land use.
No full-scale demonstration of this technology on the type of waste material in the M-1 Settling Basins
I has been reported.
"3 6.2.5 Alternative 8 - Chemical Fixation with Offsite Disposal
This alternative permanently immobilizes the contaminants, although the toxicity is not reduced and
the volume of the material is increased.
This alternative has fairly good short-term effectiveness. The major community impact may be air
emissions generated during excavation and fixation; however, these can be controlled by shutting down
the operation if ambient air and wind monitoring indicate a possible threat. Some risk may be
associated with transporting the chemically fixed materials to the offsite disposal facility. Any risks to
workers during implementation can be addressed by using common personal protection and site safety-
hazard prevention techniques.
The long-term effectiveness of this alternative is good because the contaminants are permanently
immobilized.
No full-scale demonstration of this technology on the type of waste material in the M-1 Settling Basins
has been reported.
63 CONCLUSIONS
Alternative 6, In-situ vitrification, is the preferred alternative. In general, a treatment alternative is
preferable to a containment alternative at this site because the source volume is known, the wasic
characteristics are well-defined, there are high concentrations of contaminants, and because the source
is obviously and actively contaminating groundwater. The advantages of in-situ vitrification are that the
metals are either immobilized or recovered and that any organic contaminants are destroyed, thereby
reducing the toxicity of the material.
6-7(11111CO2.3100) (11/18/39)
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Although the cor.(ainment alternatives are less costly, the treatment costs during any subsequent final
remediation would increase due to the increased volume of material that would then include the
containment construction materials. Chemical fixation with onsite storage is a less expers~ve treatment
technology, but again the chemically fixed materials, as well as the landfill construction materials, mayneed to be moved during the final remedy. Chemical fixation with offsite disposal is as -.)stly as the in-
situ vitrification, but it does not have the advantage of actually destroying the organic contaminants and
could result in some short-term impacts during initial excavation activities.
UUIIIIIIIIII
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* 7.0REFERENCES
n Brochine. Undated. "Procestechnologie, Heidemj Uitroering."
Considine, Douglas M. 1974. Chemical and Process Technology Encyclopedia.
Costa, J.E., Bilodeau, S.W. 1982. Geology of Denver, Colorado, United States of America. "Bulletin of theAssociation of Engineering Geologist," Vol. XIX, No. 3.
DeVoto, R.H. 1968. Quaternary History of the Rocky Mountain Arsenal and Environs, Adams County,Colorado: Quarterly of the Colorado School of Mines.
Ebasco Services, Inc. 1987. Final Technical Plan, Program for Army Spill Sites, Phase I. Volume I. Version 3.2,Task No. 24. November 1987. RIC 88286R06.
Ebasco Services, Inc. 1988. Final Phase I Data Presentation Report, Army Spill Sites, South PlantsManufacturing Complex, Task No. 24, Version 3.2. September 1988. RIC 88286R10.
Ebasco Services, Inc. 1989a. Proposed Final Remedial Investigation Report, Volume VIII, South Plants StudyArea, Section 1.0. June 1989. RIC 89166R04.
Ebasco Services, Inc. 1989b. Draft Final Remedial Investigation Report, Central Study Area. Version 2.1.March 1989. RIC 89166RO6.
3 Environmental Protection Agency. 1988. Guidance for Conducting Remedial Investigations and FeasibilityStudies under CERCLA. EPA/540/6-89-004.
Environmental Protection Agency. 1989. SITE, Solidification/Stabilization Process. March 1989.EPA/540/M5/89/001.
Environmental Science and Engineering, Inc. 1988. Sump 1727 Interim Response Action AlternativesAssessment, Final Report, Version 3.2. July 1988. RIC 88243RO1.
Evans, D.M. 1966. The Denver Area Earthquakes and the Rocky Mountain Arsenal Disposal Well. "TheMountain Geologist," Vol. 3, No. 1.
Hansen, W.R., Crosby, E.J. 1982. "Environmental Geology of the Front Range Urban Corridor and Vicin-ty,Colorado.* U.S. Geological Survey Professional Paper 1230.
I Haun, J.D., Kent, H.C. 1965. Geologic History of the Rocky Mountain Region. "Bulletin of the AmericanAssociation of Petroleum Geologists," Vol. 49, No. 11.
Lindvall, Robert M. 1980. Geologic Map of the Sable Quadrangle, Adams and Denver Counties, Colorado.
May, J.H. 1982. Regional Groundwater Study of Rocky Mountain Arsenal, Denver, Colorado: U.S. ArmyEngineer Waterways Experiment Station.
Romero, J.C. 1976. Groundwater Resources of the Bedrock Aquifers of the Denver Basin, Colorado: Denver,Colorado Department of Natural Resources, Division of Water Resources.
n Scott, G.R. 1960. Subdivision of the Quaternary Alluvium East of the Front Range near Denver, Colorado:Geologic Society of America Bulletin, Vol. 71, No. 10.I
7-1(I 1llC2.-3n) (11/1a/U) (UOMA)
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U Woodward.Clydeo
i Sonneberg, S.A. 1982. The Lanyard Field, A Structural-Stratigraphic Trap, Denver Basin, Colorado: "TheMountain Geologist.* Vol. 19, No. 3.
Stollar, R.L. & Associates, Comprehensive Monitoring Program: Annual Groundwater Report, V. 1
Weimer, RJ. 1973. April. A Guide to Uppermost Cretaceous Stratigraphy, Central Front Range, Colorado:Deltaic Sedimentation, Growth Faulting, and Early Laramide Crustal Movement. "The Mountain Geologist, 'Vol.10, No. 3.
Woodward-Clyde Consultants. 1989. Results of Field and Laboratory Investigations Conducted to Evaluate3 Interim Response Actions for Other Contamination Sources.
Zimpro, Inc. 1987. Personal Communication with J. Meidl and A. Withelm, Rothschild, WI.IUIIIIIIUIII
7-2
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APPENDIX ACOaMMENTS AND RESPONSES
I.
Shell Oil Company
One Snell PlazaP 0 Box 4320mHouston. Texas 77210
October 10, 1989
Office of the Program Manager for Rocky Mountain ArsenalATTN: AMXRM-PM: Mr. Donald L. CampbellRocky Mountain Arsenal, Bldg 111Commerce City, CO 80022-2180
Dear Mr. Campbell:
SUBJECT: SHELL'S COMMENTS ON ALTERNATIVE ASSESSMENT FOR M-1SETTLING BASINS
Enclosed are Shell Oil Company's comn.ents on the Draft Final AlternativeAssessment of Response Actions, M-1 Settling Basins, September 1989,Version 2.0. Shell's ARAR comments are being sent under separate covertoday.
Sincerely
R. D. LundahlManager TechnicalDenver Site Project
/ajg
Enclosure
cc: (w/enclosures)Mr. Connally MearsAir and Waste Management DivisionU.S. Environmental Protection Agency, Region VIIIOne Denver Place999 18th Street, Suite 500Denver, CO 80202-2405
Mr. Mike GaydoshAir and Waste Management DivisionU.S. Environmental Protection Agency, Region VIII999 18th Street, Suite 500Denver, CO 80202-2405
BRHM8927602 - 0001.0.0
Mr. Jeff EdsonHazardous Materials and Waste Management DivisionColorado Department of Health4210 East 11th AvenueDenver, CO 80020
Mr. David L. Shelton, Directorhazardous Materials and Waste Management DivisionColorado Department of Health4210 East 11th AvenueDenver, CO 80020
Victoria Peters, Esq.Office of Attorney GeneralCERCLA Litigation SectionOne Civic Center1560 Broadway, Suite 250Denver, CO 80202
Lt. Col. Scott P. IsaacsonEnvironmental Litigation Branch601 Pennsylvania Avenue N.W.Room 6123Washington, D.C. 20004
Mr. Robert L. DupreyDirector, Air and Waste Management DivisionU.S. Environmental Protection Agency, Region VIIIOne Denver Place999 18th Street, Suite 1300Denver, CO 80202-2405
T. KiceraAgency for Toxic Substance Disease Control8AT-TS999 18th Street, Suite 500Denver, CO 80202-2405
Dr. Peter GoberU.S. Fish and Wildlife ServiceRocky Mountain Arsenal, Bldg. 111Commerce City, CO 80022-2180
U.S. Department of the InteriorATTN: Region Environmental OfficerMr. Richard P. KruegarDenver Federal Center, Bldg. 67, Room 840P.O. Box 25007Denver, CO 80225-0007
BRHM8927602 - 0002.0.0
Director, Office of Health AssessmentsATSDRMr. Mark Bashor1600 Clifton RoadAtlanta, CA 30333
Mr. Bruce M. HuenefeldInterim Response DivisionOffice of the Program Manager for Rocky Mountain ArsenalATTN: AMXRM-IA
IC
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RESPONSE TO SHELL OIL COMPANYS COMMENTS ON DRAFT FINAL ALTERNATIVEASSESSMENT OF INTERIM RESPONSE ACTIONS. M-1 SETTLING BASINS
NOVEMBER 199
GENERAL COMMENTS
Shell Oil's major concerns vith this Draft Final Alternatives Assessment are as follows and are discussed infurther detail under Specific Comments.
Comment 1: Although this assessment asserts that the M-1 Settling Basins "appear to be" a direct source ofarsenic contamination of the groundwater, the "preliminary analytical results" which evidentlyform the basis for this statement are not provided. Meaningful comment on the site assessmentby other Organizations and the State is therefore not possible.
Response: In order to meet the mandated schedule, it was necessary to issue the Alternative Assessmentof Interim Response Actions for Other Contamination Sources, M-1 Settling Basins to theOrganizations and the State for comment prior to the validation and distribution of thelaboratory data from samples collected during the field investigation for this Task Order. Whilethe Army appreciates that this approach may have caused some confusion, it does not impactthe process. The Army views the "hot spot" investigations as a three-step process. The first stepis a field investigation to evaluate whether the M-1 Settling Basins (or other "hot spots") area source of groundwater contamination. If a "hot spot" is evaluated as being a source ofgroundwater contamination, as is the case with the M-1 Settling Basins, an alternativeassessment is developed for the purpose of evaluating the various technologies and alternativeswhich may be appropriate for mitigating any potential releases of contaminants from the M-1Settling Basins. The third step, based on the assessment of Step 2, is to select an interimaction alternative and document that decision.
Once a "hot spot" has been evaluated as being a source of groundwater contamination, Step 2can be initiated. What the other Organizations and the State are being asked to comment onin this document are the alternatives considered for mitigating potential releases of contaminantsfrom the M-1 Settling Basins. The Army believes that meaningful comments can be made onthe alternatives presented even though all data had not been validated and presented.
Comment 2: This assessment does not adhere to the Final Task Plan for Other Contamination SourcesInterim Response Actions. Specifically, the assessment proceeds to screening and evaluationof IRA alternatives notwithstanding that it fails to address the first decision node of the DecisionFlow Chart (Figure 1-1 of the Technical Plan) for "Hot Spot" IRA's; i.e., Is the site an activeprimary source (of groundwater contamination)? The site is not characterized because ofinadequate data. Pursuant to the Decision Flow Chart, the appropriate action for this sitetherefore should be monitoring (meaning additional site characterization).
Response: The Army did in fact address the first decision node on the referenced figure by stating "TheM-1 Settling Basins appear to be a direct source of arsenic contamination to the groundwater."Therefore, the answer to the first question "Is the site an active primary source?" is "Yes."Adequate data to characterize the site were collected and analyzed. At the time of publication,the data had not been fully validated and so were not included. The validated data are includedin this final report and in the Field and Laboratory Investigation Report (WCC 1989).
Comment 3: The Decision Flow Chart presented in this assessment (Figure 1-2) is an altered version of theFlow Chart actually agreed to by the Organizations and the State at the June 7, 1989 OtherCont,.mination Sources Subcommittee meeting. Specifically, Data Inadequate should be on theNQ leg of the first decision node, not on the Y_ node. The version agreed to is shown inFigure 1-1 of the final Technical Plan. This alteration appears to have misdirected this
(11111C02-3100) (11/19/89) 1
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5 assessment into an unnecessary extensive screening and evaluation of alternative remedial actionseven though the site has not been characterized by field data as an active primary source.
i Response: The Decision Flow Chart was modified to provide for a slightly more conservative path throughthe decision process in recognition of the fact that not all data were validated at the time ofpublication. The point is now moot, however, since the validated data j "wvide P 'Yes* answerto the "active primary source" question. Shell's assertion that the alteration in the flow chartleads to "an unnecessary extensive screening" is incorrect. The Army's approach was bothschedule-sensitive and cost-effective. It was based on (1) a high level of confidence in thepreliminary data, (2) the desire to eliminate costly and unneeded additional documents simplybecause of delays in data validation, and (3) the need to maintain an aggressive schedule. Theflow chart appears as originally agreed to in this final assessment.
Comment 4: This assessment gives insufficient weight to objectives and guidelines set forth in the FederalFacility Agreement and the Technical Program Plan (FY88-FY92) for IRA's, emphasizinginstead the guidelines of CERCLA Section 120. Consequently, the assessment is biased towardtreatment alternatives which are better suited for consideration in the Final Remedy rather thanas interim response actions. The intention that IRA's provide early response actions utilizingcost-effective, proven technologies to mitigate the threat of releases is subordinated to the longerterm remediation goals of CERCLA. Many of the treatment alternatives which survivedscreening in this assessment would require considerable time for either or both developmentand demonstrating effectiveness on the RMA or implementing the treatment technology. Theyalso pose the risk of not being consistent with the Final Remedy.
Response: The Army agrees that it may be desirable to give increased weight to Federal Facility Agreementand Technical Program Plan guidance. The effects of this change in weight will be most evidentin Section 6.0, which presents a preliminary ranking of alternatives. It is emphasized that thisis an alternative assessment, not a decision document, and it is necessary to assess all options,including no action, institutional controls, containment, and treatment in order to evaluate whichalternative best meets the objectives of the IRA. A revised ranking is presented in this finalassessment.
The treatment technologies presented as alternatives in this assessment have undergonefeasibility testing. Consistency with the final remedy is one of the criteria evaluated in Section6.2.
Comment 5: Groundwater treatment is not considered in this assessment except as it may be used indewatering operations. The logic for this is not very clear in the text but may be based on thepremise that groundwater remediation is beyond the scope of this IRA. While this is a correctpremise, rejection of groundwater treatment as a technology option ignores the fact thatgroundwater interception and treatment is an effective containment strategy with favorableaspects with respect to the IRA objective and guidelines as set forth in the FFA and TPP. Infact, this strategy is widely employed on the RMA. All existing and pending groundwaterintercept/treatment systems on the RMA are justified on the basis of containment, notremediation of groundwater.
Response: The Army acknowledges that many IRAs employ groundwater interception and treatment asa containment strategy. However, this was considered during alternative development andrejected at the M-1 Settling Basins on the basis of the maintenance associated with an extractionand treatment system, and of the sludge handling problems that would occur because of the higharsenic concentrations in the groundwater at this site. Other alternatives are available that canmitigate releases from the M-1 Settling Basins without significant long-term operations andmaintenance, and without generating secondary waste streams which are difficult to handle.
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Comment 6. The focus of this assessment is blurred because the text confuses objectives with remedial actionstrategies and CERCIA guidelines and criteria (Section 3.1). Consequently, in Shell's opinion,a large amount of the work performed in this assessment is misguided and unnecessary. Thesingle objective of this IRA is provided in the Technical Program Plan, Section 33.2.7, to wit:Mitigate the threat of releases from selected "hot spot" (M-1 Settling Basins) contaminationsources. This objective, which was agreed to by the Organizations, should be the focus of bothalternative development and evaluation.
Response: The text has been changed to be consistent with the wording of the Technical Program Plan,Section 3.3.2.7. However, this does not affect the subsequent technology screening andalternative evaluation, since the major objective of the proposed interim action has always beento mitigate the threat of release from the source.
Comment 7: Because of the foregoing, the screened list of alternatives in Section 6.0 Conclusions includestreatment alternatives, specifically 6, 7 and 8, which seem inappropriate for an interim responseaction at this site and excludes two containment strategies which seem appropriate, specificallygroundwater interception/treatment and source collection with temporary storage in a wastepile.
Response: The Army developed and evaluated a broad range of alternatives, some of which are treatmentalternatives. One of the important evaluation criteria is implementability. Alternatives whichcannot be impi.mented within a time frame consistent with an interim response action do notsurvive the screening process. Any treatment alternative which can be implemented in a timelymanner should not be considered "inappropriate" simply because this is an interim responseaction.
The Army considered two containment alternatives in its assessment. Groundwater interceptionand treatment was not considered since it includes an ongoing operating and maintenanceelement with continued waste disposal requirements.
The major existing environmental impact of the M-1 sludge material is degradation of alluvialgroundwater quality. Based on the site history and previous investigations, this sludge materialcould potentially contain lewisite or Army agent degradation products. The Army sees nobenefit in the excavation of this material only to store it, untreated, on site. There are lessexpensive containment options (slurry wall and cap) and treatment options that are better suitedto this particular site.
SPECIFIC COMMENTS
Comment 1: Pge 1-1 first paragraph.
"The M-1 Settling Basins appear to be a direct source of arsenic contamination to thegroundwater. This evaluation is discussed in Section 2.2.2."
No data are presented in Section 2.2.2 or elsewhere in this report which support this statementeven though this conclusion is used as a basis for concluding that assessment of interim responseaction alternatives is necessary.
Response: See response to Shell's General Comment No. 1.
Comment 2- Page.1-, last paragraph.
"An interim response action, as defined by this document, refers to any possible interimaction..."
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The scope and objectives of Interim Response Actions implemented for remediation of theRMA are defined in the Federal Facility Agreement (FFA) and the Technical Program Plan(TPP) and are the result of considerable discussions between the Organizations and the Stateand have been agreed to by the Organizations. It is therefore improper to conduct thisAlternative Assessment on the basis of how an Interim Response Action is *defined in this(Alternative Assessment) document", unless the definition agreed to by the Organizations andthe State is used. As discussed in General Comments, this assessment is misdirected due inpart to a failure in recognizing the objectives and guidelines for IRA's as set for.h in the FFAand the TPP.
The phrase "as amended by the Superfund Amendments and Reauthorization Act of 1986"should be added before "(CERCLA)".
Response: The IRA Alternative Assessment has been conducted in accordance with the Federal FacilityAgreement and the Technical Program Plan. The text has been changed to better reflect this.
Comment 3: Page..-4, second paragraph.
"The type of action taken, either long-term monitoring or interim treatment..."
The choices are not limited to monitoring or treatment. The objective of the Remediation ofOther Contamination Sources IRA is stated clearly in the Army's Technical Program Plan at3.3.2.7: "Mitigate the threat of releases from selected "hot spot" contamination sources."Consistent with this objective, the intent of RMA IRA's is to prevent the worsening of problems,i.e., increase in cost of, or time required for, the Final Remedy. It is not to remediate sites,although remediation to acceptable levels may result. Considering emphasis on timelyimplementation of IRA's, this objective will usually be best met by a containment or isolationaction. In some cases, treatment may facilitate containment or isolation. The focus howevershould be on preventing the spread of contamination, not on remediation.
Response: It is agreed that the objective of the IRA is to mitigate the threat of releases from the site.However, it is appropriate to evaluate a range of alternatives in order to meet this objective,not excluding treatment alternatives. The text has been changed.
Comment 4: PaUe 1-4, third paragraph.
"If the answers to the questions on the decision flow chart are inconclusive, aconservative approach will be taken. For example, if a clear risk to human or biotareceptors has not been shown, it will be assumed that some risk exists."
There are several serious misrepresentations in this statement which in part cause thisassessment to be misdirected.
First, the issue involved here is not one of conservatism of approach to an interim responseaction, but is simply a matter of the da&.• being inadequate to perform an assessment. Toproceed with a specific action with inadu'qu..e data risks wasting valuable resources on workwhich may not protect the environment c: human health, even in fact do harm, and may notbe consistent with the Final Remedy.
Second, it was not agreed that if data are inconclusive or inadequate, a conservative approachwould be taken. The agreement reached by the Organizations and the State in the June 7, 1989Subcommittee meeting was that inadequate data would trigger the monitoring/maintenanceaction. Monitoring/maintenance may include further site investigation. The Decision FlowChart in this assessment (Figure 1-2) is an altered version of the flow chart agreed to and whichappears as Figure 1-1 in the Final Task Plan for Remediation of Other Contaminant SourcesInterim Response Action. Specifically, the Data InadeJuate decision path has been moved from
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the NO to the ME pathway. Figure 1-2 of this assessment document should be replaced bythe agreed to version. Data presented on this site are inadequate to assess the question ofwhether the M-1 Settling Basins are an active primary source of groundwater contamination.Accordingly, before proceeding with screening and evaluation of technology alternatives, furthersite investigation should be conducted.
Response: See response to Shell's General Comment No. 3.
Comment 5: Pge 1-4, fourth paragraph.
"...there may be some benefit in performing an IRA now. ...The benefit in performingany of these actions will be discussed in the IRA Decision Document.*
If the reason for considering an interim response action for this site is a possible long termbenefit to cost or timing of RMA remediation, how can a meaningful discussion of alternativesbe achieved if these possible benefits are not addressed? Clearly, achievement of a long termbenefit in cost or timing should be a primary consideration and criterion in the developmentand evaluation of alternatives.
Response: Agreed. These issues are discussed in greater detail in Section 6.2 of the final alternativesassessment.
Comment 6: P , third paragraph.
The structures presently on and near tb- M-1 Settling Basins were used in the manufacture ofbicycloheptadiene (BCH) which is not an insecticide. BCH is an intermediate in themanufacture of aldrin and dieldrin. BCH operations terminated in 1974 and these structureswere not used thereafter.
Response: The text has been changed.
Comment 7: Pgi2-, last paragraph.
Aquifer tests in the alluvial and Denver Formation aquifers have shown the hydraulicconductivities to vary much more than the ranges listed in this paragraph.
Response: The text has been changed.
Comment 8: Page.2-, second paragraph.
In Table 2-2, the concentrations of several organic contaminants in groundwater are significantlyhigher in downgradient wells than in upgradient wells. These contaminants includebicycloheptadiene, chloroform, chlorophenylmethyl sulfone, dicyclopentadiene, dieldrin, anddiisopropylmethyl phosphonate. These data indicate that the M-1 Basins could be a possiblesource of these contaminants. Did the spring 1989 sampling program include only arsenic andmercury as analytes? The two new wells (01083 and 36193) are favorably located for providingupgradient/downgradient water quality data. Analysis of a comprehensive analyte suite for thesewells would enhance the site investigation.
Response: The Army agrees that the M-1 Settling Basins could be a source of the above-mentionedcontaminants. The 1989 sampling program did include only arsenic and mercury as analytes.However, additional site characterization would not have affected the decision that the M-1Settling Basins are a source of groundwater contamination. Also, the alternatives assessmentwould not have been affected by additional site characterization because the possible presenceof organic contaminants was considered during the screening of alternatives.
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Comment 9:. PEags2-, last sentence.
Well No. "10183" should be "01083."
Response: The text has been changed.
Comment 10- Page.2-, first paragraph.
The physical form of the mercury contamination should be indicated, i.e., mercury salts (solid)or elemental mercury (liquid), since the physical state is an important criterion in the evaluationof the remediation technologies.
Response: The analytical methods used during site characterization reported mercury concentration in thesludge without regard to its physical/chemical form. The site history relates the fact that spentmercuric chloride catalyst was disposed of in the basins. Whether or not mercury still exists inthis form is unknown. The chemical state of the mercury could affect the effectiveness ofchemical fixation. Treatability testing of that technology would be required.
Comment 11: Pgg 2-, second paragraph.
The interpretation that high concentrations of arsenic are being transported by attachment tosoil particles moving with the groundwater may be in error. Basing this interpretation on thedifference in the concentration of arsenic between filtered and unfiltered groundwater samplesfrom Well 01503 and 01504 is not advisable because of the proximity of the wells to the M-1Basins. Monitoring well sampling procedures can mobilize soil particles near the wellbore; thus,the presence of sediment in groundwater samples may not be representative of normal aquiferconditions. Because these wells could be located within a few feet of the sludge, the higharsenic concentrations in the unfiltered samples from these wells do not necessarily indicatethat significant arsenic migration by this mechanism is occurring.
How far downgradient do high concentrations of arsenic persist?
Response: Agreed. The interpretation of the difference between filtered and unfiltered sample arsenicanalyses has been revised based on results of the 1989 field investigation. Please see the revisedtext in Section 2.2.2.
Arsenic concentrations were found as far north as the Lime Settling Basins. At that point,arsenic contamination from the Lime Settling Basins occurs. It is difficult to determine whatportion of the arsenic contamination downgradient of the Lime Settling Basins is actuallyattributable to the M-1 Settling Basins.
Comment 12: EUg2J, third paragraph.
How do you reconcile the observations that in previous sampling very little of the arsenic wasin soluble form and in 1989 sampling almost all arsenic was in soluble form? If standardizedsampling procedures were used and background aquifer conditions (Eh and pH) were relativelystable, the total/dissolved ratio should not have changed so drastically.
If the "high concentration of arsenic immediately downgradient of the M-1 Settling Basins" wasobtained from Well 01503 or 01504, it is questionable that significant migration of arsenic hasoccurred. These wells are located near the basins and could be within a few feet of the sludge.Without providing the spring 1989 data, the distribution of arsenic is unknown and theconclusion that the "M-1 Settling Basins are a direct source of groundwater contamination" isalso questionable. The pre-1989 water quality data in Table 2-2 also do not support the Army's
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conclusion because no upgradient data were included. Further investigation is needed to decidewhether this site is a primary active source of groundwater contamination.
Response: We cannot reconcile the conflicting observations. Different sample preparation or preservationmethods may have been used.
The spring 1989 data clearly show arsenic concentrations to be higher downgradient of the M-1Settling Basins than upgradient. Wells 36001 and 36193 were also sampled, whi,;h are furtherdowngradient of the M-1 Settling Basins. These data have been included in Table 2-2 of thefinal alternatives assessment and are discussed in detail in the Field and Laboratory Investigation
Report (WCC 1989).
Comment 13: Page 2- , third paragraph.
This paragraph states that "preliminary" analytical results from groundwater sampling conductedin Spring 1989 indicates that the M-1 Settling Basins are a direct source of groundwatercontamination. However, these data are apparently not presented in this report. If these datawere considered sufficiently reliable to trigger the extensive engineering work performed in thisassessment, why can't they be published in this assessment document? In accordance with theDecision Flow Chart, pending a determination on whether or not the M-1 Settling Basins arean active primary source, development of response alternatives should not have been begun.
An adequate site assessment is an essential predicate for the development and screening oftechnology alternatives. Data on, and interpretation of, contaminant concentrations in thebasins, as well as in up- and down-gradient groundwater, are a requirement. The otherOrganizations and the State cannot provide meaningful comment when primary data which issaid to "indicate" that this site is an active primary source are not shown.
The profile of groundwater contamination in Table 2-2, coupled with the history of these basins,strongly suggest that other sources contribute to groundwater contamination in the area aroundthese basins. The close proximity of the basins to the old chemical sewer line (Figure 1-1)suggests one likely source.
Response: See responses to Shell's General Comments Nos. 1, 2, and 3. The validated data is presented
in the final alternative assessment.
Comment 14: Page 2-6, 2.3 Contaminant Fate and Transport
This Section, which is very general and theoretical (with respect to this specific site), could serveas an introduction to an assessment of the site data to address the question of whether or notthe M-1 Settling Basins are an active primary source. However, it does not constitute a siteassessment.
The last sentence of the first paragraph states: "This section presents the fate and transport ofboth the organics and metals detected in these field investigations." This should be revised tostate that possible mechanisms for fate and transport at this site are discussed.
Contaminants whose source(s) are upgradient of the basins should not be included in thisdiscussion. They are beyond the scope of this IRA.
The brevity and simplicity of statements in this Section raise questions as to its value to thisassessment. For example, the whole discussion (23.1.1.2) of volatilization of semivolatilechlorinated hydrocarbons is:
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"The semivolatile chlorinated hydrocarbons are somewhat volatile (Table 2-3) and couldbe lost by volatilization into the atmosphere. These compounds are more volatile thanthe pesticides."
Response: This section has been revised.
Comment 15: Pag. 2-, Section 2.3.1 - Fate of the Oranics.
We suggest that the discussion in this section be divided into two sections: (1) a discussion ofthe fate and transport of the contaminants in soils, and (2) a discussion of the fate and transportof the contaminants in groundwater. Also, at some point in this section, the Army shouldprovide pH data for the soils in the M-1 Settling Basins.
Response: The text has been changed. According to the South Plants Study Area report, the pH of soilsin the South Plants Area ranges from 6.3 to 9.0. The site history of the M-1 Settling Basins andthe pH levels found during groundwater sampling seem to imply that the soils in the immediatevicinity of the M-1 Settling Basins are most likely alkaline.
Comment 16: Page .2-, Section 2.3,1.1 - Volatilization.
The volatilization process in incorrectly stated for the following reason:
The volatilization of organic compounds from soils is dependent on several factors,including soil temperature and moisture content, vapor pressure, solubility of thecompound in water, compound concentration, the ability of two or more contaminantsto form azeotropic mixtures, air flow over the soil surface, humidity, sorptive anddiffusion characteristics of the soil, and bulk properties of the soil such as organicmatter content, porosity, density, clay content and clay mineralogy. All of these factorsaffect the distribution of a compound between soil, soil water, soil air, and theatmosphere.
Response: The text has been changed.
Comment 17: Page 2-6, fourth paragraph.
Aldrin and dieldrin were not detected in the M-1 Basin sludge (Table 2-1); therefore, the M-1Basins are probably not a source of these compounds.
Response: The text has been changed to focus on compounds that were consistently detectible in the M-1sludge and over burden soil
Comment 18: EgL.272, fourth paragraph.
A reference should be provided for the statement that chloroform has a half-life of 3,500 years.
Response: The statement has been deleted.
Comment 19. P.&g.2-, first paragraph.
Aldrin and dieldrin are not the only compounds present for which plant uptake is expected.Cadmium is readily adsorbed by plants. The arsenic concentration in plants varies between 0.01and 1.0 ppm (Brown, *Hazardous Waste Land Treatment," at 242). Moreover, very little if anyaldrin and/or dieldrin may be adsorbed by native plants if the oil content of the plants is low.
Response: Discussion of aldrin and dieldrin has been deleted from the revised text. However, with thesmall amount of plant life at the site, plant uptake is probably insignificant.
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IComment 20. age 28, second paragraph.
Biodegradation takes place with some species of fungi as well as some bacteria.
Response: Agreed. The text has been changed.
Commcnt 21: Page.2-, Sections 2.3.1.6.1 througlh 2.3.1.6.3.
The rate of biodegradation of organic compounds in nature is a function of several factorsincluding the structure of the compound, soil temperature, and soil physiochemistry. Thebiodegradation of benzene in soils is rapid, but the biodegradation of carbon tetrachloride isslow. The use of biodegradation to destroy a contaminant requires a specific organism to attacka specific compound under suitable environmental conditions.
I Response: Reference to South Plants alluvial groundwater contaminants has been deleted in the revised
text.
Comment 22: Pag.2-•,1 , first paragraph.
Through the text, "adsorption" is incorrectly referred to as "Pbsorption."
Why are only lignite seams in the Denver Formation a hindrance to migration of organics?Wouldn't claystones in the Denver Formation have a similar effect?
* Response: The text has been changed.
Comment 23: Page..1,, fourth paragraph.
Evapotranspiration is the dominant fate of precipitation at RMA. Infiltration is normallyminor except during intense storms or where it is enhanced such as by drainage ditches, catchbasins, etc.
Response: The text has been changed. However, some infiltration is still expected to occur given the natureof the sandy soils at the site.
Comment 24: EUagL.2_., second paragraph.
Evapotranspiration is the dominant fate of precipitation at RMA; however, infiltration is themajor pathway from a contaminant transport perspective.
S Response: Agreed.
Comment 25: Pga.e2-11, third paragraph.
Aldrin and dieldrin transport with rainwater to the groundwater is possible, but based on theadsorption coefficients this transport mechanism is not very likely.
Response: Reference to aldrin and dieldrin has been eliminated in the revised text.
Comment 26: PEgc.2-11, fourth paragraph.
At the low concentrations of hexachlorocyclopentadiene detected, it is not likely that its highdensity affects its downward migration rate.
Response: Agreed. The text has been changed.
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Comwent 27: gL.,.,, first paragraph.
Soluble organics can migrate with the groundwater, but it should be pointed out that eachcompound has different retardation factors. Migration will vary widely for this list ofcompounds.
Response: Agreed. The text has been changed.
Comment 28: PFage2,12, first paragraph, second sentence.
"(G)roundwater gradient" should be "groundwater migration rate.'
Response: The text has been changed.
Comment 29: EU&g "-, second paragraph.
"Bicycloheptadiene and dicycloheptadiene are highly volatile (Table 2-3)."
It is not accurate to describe these compounds as highly volatile.
Response: The text has been changed.
Comment 30. Pag.2.12, third paragraph.
High solubility and low sorption are much more important than volatility for movement ofchemicals down to and through the Denver Formation.
Response: Agreed. The text has been changed.
Comment 31': Page2-1 , Section 2.3.3.
While in general metals remain predominantly in the soils over time, a particular metal may beoxidized or reduced to a different species. For example, arsenic in soils is converted to arsenatesexcept under highly reducing conditions. Arsenate ions are readily sorbed by hydrous oxidesof iron and aluminum and thus leaching of arsenate is slow. Arsenic behaves much likephosphorus in soils in that adsorption of arsenic increases as iron oxide content increases. Allof the arsenic halides are covalent compounds that hydrolyze in the presence of water. EPA,"Ambient Water Quality Criteria Document: Arsenic at 3.
Moreover, the National Research Council of Canada reports that the half-life of arsenic trioxidein soils is 6.5 years, but the half-life of lead arsenate is 16 years. The loss of arsenic from thesoils over time must be accounted for by the transport of arsenic to other media.
In aerobic water, inorganic arsenic (Ill) is slowly oxidized to arsenic (V) at neutral pH, but thereaction proceeds measurably in strongly acidic or alkaline solutions. EPA, "Ambient WaterQuality Criteria Document: Arsenic.'
A similar discussion could be presented for each of the metals present in the M-1 basins, butthe point of the matter is this: the fate and transport of metals in this paragraph and section2.3.4 are addressed in a superficial fashion.
Response: The text has been changed.
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Commeat 32: Fagg_2,,3, Section 2.3.4.
The term "nonsolubic" should be replace with "insoluble." This paragraph is over generalizedto the point of being erroneous. For example, some metal oxides, such as chromium (VI) oxide,mercuric oxide, and arsenic pentoxide, are soluble in water. Humic metal complexes haveconditional stability constants that vary with pH, and follow the Irving-Williams series. Ingeneral, the stabilities of aquatic humic complexes follow this order for the metals present atthis sit•.:
Hg> Cu >Cd
See E. M. Thurman, "Organic Geochemistry of Natural Waters," at 415. Given the conditionsat this sitc, some of the metals may not be sorbed on the surface of humic material (if humicmaterial is present).
Response: The text has been changed.
Comment 33: Page 2-14, first sentence.
Soil erosion is more related to soil type and condition, vegetative cover, and precipitationintensity than it is to annual precipitation.
Response: Agreed. The text has been changed.
Comment 34: Pape 2-14, first full paragraph.
Total Threshold Limit Concentration (TTLC) is a criterion used only in California and istherefore not appropriate for use at RMA.
Response: Agreed. The text has been changed to eliminate this reference.
Comment 35: Page_2,14, second paragraph.
Infiltration to groundwater is not a very significant pathway at RMA without some mechanismof recharge enhancement.
Response: Intermittent infiltration is a possible pathway at Rocky Mountain Arsenal.
Comment 36: Page 2-14, paragraph under 2.4.
"With the available knowledge of the nature and distribution of chemical contaminantsat the site as well as the fate and transport of these chemicals in the environment, asurvey of applicable or relevant and appropriate regulations (ARARs) :., n.cesiy."
This statement is misleading if it is meant to imply that the prior Sections have established thatthe M-1 Settling Basins are an active primary source of groundwater contamination. Since thishas not been done, it is suggested that this statement be deleted or modified. There has beenpractically no kr.: wledge in the form of data presented in these Sections.
Response: See response to Shell's General Comment No. 2.
Comment 37: P , third paragraph.
"No aquifer dewatering and subsequent treatment will be necessary for the purpose ofthis interim response action."
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Please explain the rationale for this statement and why this assumption is necessaryGroundwater interception/treatment is a cost-effective containment strategy' which has beenselected as tLe alternate of choice in several other IRA's and all three boundary control systemson the RMA.
Response: See response to Shell's General Comment No. 5.
I Comment 38: Table 2- Summar of Contaminants in Groundwater.
The only data presentation in this assessment bearing on possible migration of contaminantsfrom the M-1 Basins to groundwater is this table. The simple listing of concentration rangesupgradient and downgradient is an inadequate basis for aatempting to interpret whethercontaminants are migrating from this site, e.g., there is no indication as to the date or locationof samples. Moveover, most all of the compounds listed are in greater concentration ungadientthan d. While the text justifies proceeding with an interim response action on thebasis that arsenic is migrating to groundwater from this site, only two arsenic analyses arereported in this key table, both on downgradient samples. A more thorough presentation ofdata and date interpretation is required to justify more than monitoring for this IRA. The"preliminary" 1989 data should be included.
Response: The purpose of this document is to develop and evaluate IRA alternatives. Data used tocharacterize the site can be iound in previous documents (Army Spill Sites Data PresentationReport [Ebasco 1988], South Plants Study Area Reports [Ebasco 1989b] and in the RMA database). Therefore, this document did not repeat the information contained in these documents,in other than summary form. A detailed analysis of the 1989 data can be found in the Field andLaboratory Investigation Report (WCC 1989).
Comment 39. Table 2-2.
This table lists incorrectly the chemical names for DDE and DDT.
Response: The table has been corrected.
Comment 40: Table 2-3.
The title of this table should indicate that the information provided is for soil contaminants inthe M-1 basins. Also, the physical properties for all of the compounds listed in Table 2-1 shouldbe listed here as well.
Response: The text has been changed to eliminate reference to this table. The reference is now the SouthPlants Study Area Report (Ebasco 1989a).
Comment 41: Table 2-3. Chemical and Physical Properties of Organic Anal•tes in the M-1 Settling Basin Area.
Please add methylene chloride, chloroform, CPMSO2, and DIMP to this table.
Response: See response to Shell's specific comment No. 40. The physical properties of these analytes arelisted in the South Plants Study Area report.
Comment 42: E"igtr2.1, M-1 Basins Field Program.
Please explain the significance of MITI through MIT6. MITI is labeled as a trench in thefigure but is not mentioned in the text.
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I Response: The figure has been revised for clarification. MITI through M1T6 were exploratory trenches.Additionally, soi/sludge samples for the ISV treatability test were samples taken from M1T3and MIT6.
Comment 43: Pape 3-1, Section 3.0 Identification and Evaluation of Interim Action Technologies.
This assessment is biased toward a final remedy solution because it fails to recognize guidelinesand objectives set forth by the Organizations in the FAA and TPP concerning conduct of IRA'son the RMA. Specifically,
3 • TPP. Section 3.3.2.7
Remediation of Other Contamination Sources.
Objective: Mitigate the threat of releases from selected "hot spot"contaminationsources.
3 • TPP. Section 3.1
IRA's are "removal" actions.
n • FFA. Section 22.5
All IRA's shall...to the maximum extent practicable be consistent with and contributeto the efficient performance of Final Response Actions.
FAA, Section 22.6
The goal of the (IRA Alternative) assessment shall be to...select the most cost-effectivealternative for attaining the objective of the IRA.
• FFA 2,.a)
I Provide for IRA's which are appropriate for the Site prior to implementation of finalremedial action(s) for the Site.
IRA's are intended to be implemented on a timely basis, otherwise the benefit of taking anaction prior to implementing the Final Remedy is diminished or lost. Proven, off-the shelftechnologies facilitate this intent. The goal is to quickly implement the most cost effectiveresponse that will mitigate a threat of release of contaminants. The objective is clearly notremediation, although a remediation alternative is not excluded if it best meets IRA andCERCILA guidelines.SThere is almost no prominence given in this assessment to these IRA objectives and guidelines.Rather, the assessment has been incorrectly conducted using CERCLA guidelines for a final
remedy.
5 Response: See response to Shell's General Comment No. 4.
Comment 44: Pagc..-1, first paragraph.
3 The second sentence of this paragraph causes this Section and Sections 4.0., 5.0 and 6.0 to bemisdirected.
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"The interim response action objectives are site-specific goalsfor treating soil to protect human health and theenvironment."
The objective of this IRA is to mitigate the threat of releases from the M-1 Basins (TPP,Section 3.3.2.7). The assessment in Section 1-2, developed the goal of creating a long-termbenefit in cost or timing for RMA final remediation of this site. Accordingly, alternates shouldbe developed and evaluated with this site-specific goal uppermost in mind. Treating the soilmay be a strategy to achieve this goal, but it is not the objective of the IRA. Protection ofhuman health and environment is one of the criteria against which the expected performanceof an alternative is evaluated.
Response: The wording of the objective has been changed to more closely adhere to the TechnicalProgram Plan.
Comment 45: Pag.3-1, third paragraph.
The first bullet is the objective. The other bullets are evaluation criteria The goal of reducingthe cost of the Final Remedy should play a prominent role in the identification and evaluationof alternatives.
Response: The wording of this section has been changed to more closely adhere to the Technical ProgramPlan.
Comment 46: Pg .-, second paragraph.
"Water treatment would only be conducted as part of a dewatering operation requiredfor a soil/sludge treatment. The objective (sic) of this interim response action issource containment, removal, or treatment."
The only objective of this IRA is stated at 3.3.2.7 of the TPP. The objective is not to select acertain type of technology. This assessment consistently confuses objectives and strategies(what is expected to be accomplished versus how it will be accomplished).
The logic of the statement that water treatment would only be conducted as part of adewatering operation is not at all clear. Groundwater interception/treatment is a widely usedstrategy for mitigating releases from source sites and is widely practiced on the RMA, includingas interim response actions.
"Groundwater remediation is assumed to be beyond the scope of this IRA."
Agreed. However, this does not exclude using groundwater interception/treatment as a strategyto contain releases from a hot spot.
Response: See response to Shell's General Comment No. 5.
Comment 47: Ea.cg.:, first paragraph.
"Tables 3-1a and -lb list generpi response actions and associated technologies typicallyapplied to contaminated soil and associated groundwater."
Rather than starting with a list of general response actions, this assessment could be betterfocused by considering possible strategies for meeting the specific IRA objectives for thisspecific site and then developing alternatives based on technologies appropriate for these
strategies.
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Response: The Army considered it appropriate to look at a wide range of strategies, and to carry throughalternatives associated with each of these strategies. Consequently, the approach was todescribe to the reader applicable technologies, and then use these to develop the desired widerange of alternatives.
Comment 48: Ag,3-4, last paragraph.
To the list of containment technologies should be added groundwater interception, treatmentand reinjection. This is a practical containment strategy as is demonstrated by control systemspresently in operation on the RMA.
Response: See the response to Shell's General Comment No. 5.
Comment 49. Page..-, last paragraph.
Surface capping does not necessarily need to be used in conjunction with other groundwatermeasures to be effective in reducing contaminant leachate production from near-surface soils.
Response: Agreed. The text has been changed to clarify this point.
Comment 50: P~age.3-, fourth paragraph, last sentence.
A surface capping system can be very effective in some circumstances even if not constructedin conjunction with a slurry wall.
Response: Agreed. A surface cap is carried through as Alternative 5.
Comment 51: Page 3-6, 312.3.U.
How would potentially contaminated soils generated during slurry wall construction be handled?This could dramatically increase the cost of slurry wall construction, thus making grout curtainsor sheet piles more cost-effective. If an inexpensive method of dealing with excavated soils isnot readily apparent, either sheet piling and/or grout curtains should be retained for furtherconsideration.
Response: Potentially contaminated soils excavated during slurry wall construction will be placed withinthe slurry wall and used in regrading the site to control runon and runoff before capconstruction.
Comment 52- EUg3&, first paragraph.
Sheet piling may or may not be more expensive than a slurry wall; it depends upon the site andthe situation.
Response: Agreed. However, sheet piling may be less effective at this site than a slurry wall because ofthe sandy soils, which could prevent sealing between the plates and could therefore result in anineffective contaminant system.
Comment 53: Page.3-, 3.2..T1reatment.
The text should explain why treatment is considered as part of an interim response strategy.Will dedicated treatment processes be implemented for all individual IRA sites? This wouldnot be cost-effective and may not be consistent with final remedial actions. Most of thetreatment technologies discussed in this Section seem unsuited for an interim response action
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because substantial development and site-specific testing would be required with the prospectthat such testing will determine that a technology is not feasible or is not cost-effective.
Response: Treatment technologies considered as IRA alternatives for the M-1 Settling Basins (in-situvitrification and chemical fixation) have already been bench-tested using M-1 Basin sludge.Nothing in the Federal Facility Agreement or the Technical Program Plan precludes theconsideration of treatment technologies. Only treatment technologies which would meet theIRA objective to mitigate the threat of release from the source are developed into alternatives.I Treatment alternatives undergo the same evaluation as other alternatives with regard toimplementability, timeliness, cost-effectiveness, and consistency with the final remedy to themaximum extent practicable.
Comment 54: fa&_3.-, Section 3.2.5.1.1 - In-situ Vitrification.
The sediment/sludge in the settling basins is rich in lime. The lime is refractory and mayrequire much higher temperatures unless it is mixed with other components to reduce slaggingtemperatures.
Response: Bench testing has shown that a melt can be maintained at temperatures between 1600 * and
1700" C.
Comment 55: Pan 3-10, first paragraph.
Arsenic and mercury would be volatilized by in-situ vitrification and would need to be collectedalong with any volatile organics or byproducts.
Response: Agreed. The text has been changed.
Comment 56: Page3-1.Q, fourth paragraph.
Chemical fixation is known to work better on metals than organics.
Response: Agreed. Metals are the primary contaminants at the M-1 Settling Basins.
Comment 57: EAgL: Sci, .
The matrix is lime-rich, so pH is already high.
Response: Agreed. However, this section was meant to be a general introduction to the process.
Comment 58: EUgLL.1U, Sction 3.2..22.
How are metals leached from high lime sludges without extreme reagent additions?
Response: Agreed. The text states this on page 3-14, paragraph 3.
Comment 59:- agt.,.1, last paragraph.
A major disadvantage of this technology is that a large volume of solvent (usually water)containing soil contaminants and other soluble soil constitutes is produced which must then betreated.
Response: Agreed. This technology is not considered further.
(1111IC02-3100) (11/18/9) 16
Vr ConsuftanI
Cmment6 P 60 , 3.2.5.4 Off-site Treatment.
Why is the list of possible applicable technologies different based on whether the technologyis applied onsite or offsite. Probably because of the availability of offsite facilities, however,this is not discussed.
Response: This list is limited by the availability of offsite facilities.
Comment 61: P , first paragraph.
Solidification may work for metals but has not been proven for organics.
Response: At least one program in EPA's Superfund Innovative Technology Evaluation(EPA/540/M5/89/001, March 1989) has shown promising results in the fixation of PCBs andsemi-volatile organics (EPA 1989).
Comment 62. aC 3-1, 12.7.
See comment 53.
Are seasonal changes so reliable and drastic as to be able to predict that no dewatering would
be necessary if the IRA were implemented in the dry season?
Response: Please see the discussion in response to Shell's Specific Comment No. 53.
The alternatives carried through to the final evaluation would not be greatly affected by thepresence of groundwater in the soil/sludge. The discussion of dewatering and water treatmentis included primarily as a contingency.
Comment 63: Pe3-1, Section 3.2.7.1.
If the sludges are just saturated and relatively impermeable, the use of wells or trenches is notpractical.
Response: Agreed. Dewatering processes are considered only for either dewatering the excavation orlowering the water table. None of the alternatives developed require dewatering of thesaturated sludges.
Comment 64: Page.3-1, Section 3.2.7.1.3.
Why suggest a drum filter? This is not a good application for this type of filter.
Response: A drum filter was described as one of several typical filtration methods and was not intendedto be necessarily the selected unit operation. If any type of filtration is determined to benecessary during design, the type of filter to be used will be chosen at that time.
Comment 65: Eagg=_3 , second paragraph.
Storage of groundwater for treatment in the Final Remedy should be considered in lieu ofconstructing a dedicated facility for treatment of a relatively small, discrete volume ofgroundwater. Storage volume probably already exists in the South Plants area.
Response: This option could be considered during the design phase.
(11111C02-3100) (11/18/89) 17
U WoodwardClyde Commntants
SComment 66: Page 3-, third paragraph.
Granular Activated Carbon (GAC) is currently used on the RMA site for water andgroundwater treatment and should certainly be considered for this application. Where somecontaminants are not efficiently removed by GAC, it is very common practice to couple carbonadsorption treatment with another technology, e.g., air stripping.
Response: The groundwater at the M-1 Settling Basins has contaminant concentrations several orders ofmagnitude higher than groundwater being treated by GAC elsewhere at RMA. Excessivecarbon usage rates for these high concentrations makes GAC inappropriate for this site.
U Comment 67: 3 , second paragraph.
If a technology requires process development, it is not suited for an interim response action,3 particularly if proven technologies, e.g., GAC, are available.
Response: Agreed. This technology has been removed from further consideration.
UComment 68: P second paragraph.
Rotary Biological Contractors are inefficient on chlorinated hydrocarbons as well.
3 Response: Agreed. This technology has been removed from further consideration.
Comment 69:. Page_3,28, last paragraph.
I The reason given for not considering reinjection of groundwater, i.e., dogging of well screens,is inconsistent with the fact that reinjection systems have been used in the RMA for many yearsand in most instances clogging has not been a serious problem.
Response: Use of well reinjection at RMA has been plagued with dogging of well screens in the past.Nevertheless, reinjection can be accomplished using percolation beds or trenches withoutrisking these potential clogging problems. The type of reinjection, if necessary, would bedetermined during design.
Comment 70: E"•ag:, 3.2.7.3.3 and .
I These Sections should be reviewed for consistency with the Hydrazine Blending and StorageIRA Decision Document.
Response: This document has been reviewed. A UV/oxidation system has been proposed; however, theimplementation schedule for these IRAs may not necessarily coincide.
I Comment 71: Pag&..•-, last paragraph.
The containment strategy of intercepting groundwater, treating and reinjection should be analternative considered. Also, removal and placement in a temporary waste pile, e.g., as with3 Basin F solids, would appear to be a logical strategy and should be considered.
Response: See responses to Shell's General Comments Nos. 5 and 7.
3 Comment 72- Table 4-1a. Table 6-1.
What justifies the conclusion that the No Action, Monitoring, and Institutional Controls5 alternatives are not protective of Human Health and the Environment?
5 (11111C02-3100) (11/18/89) 18
I
, iardClyd.
Response: The objective of this IRA is to mitigate the threat of releases from the M-1 Settling Basins.The M-1 Settling Basins have been evaluated as being a source of groundwater contamination.Because a threat of release to groundwater does exist, No Action, Monitoring and InstitutionalControls eo little or nothing to respond to this threat.
Comment 73: Page 4-., 4.0 Development and Evaluation of Alternatives.
The introduction to this Section ignores the objective of this IRA, the intent of IRA's and IRAguidelines as set forth in the FFA and the TPP. It also ignores the goal developed in Section1.2 of reducing the cost, or accelerating implementation, of the Final Remedy. These shouldprovide the necessary "anchor" for judgements applied in both the development and evaluationof alternatives. Without relating to them, this assessment becomes aimless.
Response: All of the alternatives developed are capable of meeting the objective of this IRA. Cost,implementability, and consistency with the final remedy are all considered during alternativeevaluation.
Comment 74: Page.3, first paragraph.
I In the absence of a site assessment which defines the contaminants emanating from the basinsand the aerial extent of groundwater impact, it is premature to specify details of a monitoringprogram, such as suite of analytes, frequency of sampling and sampling wells.
Response: Only conceptual alternative designs are presented in the IRA Alternative Assessment. Themonitoring program outlined is appropriate for the location and types of contaminants in thisarea. As with any of the alternatives, changes to the conceptual design may be made duringfinal design.
Comment 75: Page 4-3, third paragraph.
I Why is air monitoring required for non-invasive strategies? Isn't the CMP sufficient?
Response: Air monitoring has been deleted for the non-invasive strategies.
Comment 76: Page 4-4, 4.1.4.2 Construction of a Multi-layered Cap.
Why is such a complex cap required for temporary capping (see last sentence of 4.1.4)?
Response: This alternative would be designed to meet ARARs, to the maximum exvent practicable. Thiscap description is one that might typically be required for capping of hazardous waste piles.3 However, the final details of the cap design would be established during the design phase.
Comment 77: P , Section 4.1.5.
Downward percolation of rainfall on well vegetated soils on the RMA is very low. Theincremental benefits (i.e., reduced deep percolation) associated with constructing a "Multi-layered Cap" as described in this section seem very limited and probably not worth the
additional costs. Perhaps all that is warranted in this alternative is to see that a good soil cover,adequate grade for surface water drainage, and good vegetative cover are established. The costmay be much lower than constructing the "Multi-layered Cap" described, and the difference indeep percolation through the two caps would likely be insignificant.
SResponse: See response to Shell's Specific Comment No. 76.
I(i(1II11C02-3100) (11/18/89) 19
I
Woodward-Clyde ComuAwts
Comment 78& P , 4.1.6 Alternative 6.
Why is a slurry wall a part of this alternative?
Consideration would have to be given to the possibility that adverse chemical reactions couldoccur as a result of the high energy input involved.
Response: The slurry wall is used to provide a temporary barrier to groundwater recharge in thevitrification area, as is stated in Section 4.1.6.1. The need for and depth of the slurry wallwould be determined during design. The temperature gradients generated in the ISV processare very large. Ambient temperatures usually exist within one foot of thc progressing m-t.
Comment 79: P , third paragraph.
Instead of 700.000 gallons of steam. 700.000 allons of water in the form of steam is probablymeant.
Response: The text has been changed.
Comment 80: Page 4-6, third paragraph.
The described gas handling system does not appear adequate to handle the poisonous arsenic,cadmium, and mercury fumes or vapors. A wet electrostatic precipitator should be includedin the design of the system to effectively reduce the concentration of these metals in the gasstream which is discharged to the atmosphere. The off-gas stream may also contain a veryflammable mixture of organics due to the volatilization of benzene, chlorobenzene, MIBK,xylenes, etc.
Response: This document is intended to provide a ccrceptual design of each alternative. The offgassystem will be closely scrutinized during final design to be certain it will handle all possiblecontaminants in the offgas stream. The ISV process does not merely volatize the above-mentioned organics. These compounds would either by pyrolyzed in the melt or rapidlyoxidized as they migrated to the surface. A flammable mixture of organics is not anticipated.
Comment 81: P , fourth paragraph.
The condensate will also contain cadmium and a mixture of organics. However, cadmium ismore amenable to precipitation by pH adjustment than are arsenic and mercury. Due to thepresence of a yet undetermined mixture of organics, the treatment of the wastewater will likelybe difficult and not amenable to discharge to a percolation bed.
The discussion in this paragraph (as well as the previous paragraph) does not address thegeneration and disposal of solid wastes from the treatment processes. For example, thedisposal of the metals removed from the wastewater is not addressed.
Response: These details are best addressed during final design. The vast majority of cadmium will remainin the melt. Any metals that do volatize will be condensed and collected in the quench waterand scrubber water. This water would most probably be treated with a combination ofdemonstrated industrial wastewater treatment (such as pH adjustment and precipitation) andfiltration through diatomaceous earth and activated carbon. The overwhelming majority oforganics will either be pyrolyzed or oxidized during the ISV process and therefore will nothinder subsequent wastewater treatment.
(1111IC02-3100) (11/18/89) 20
Comment 82: Page 4-7, Section 4.1.7.
The chemical fixation of the wastes does not decrease the mobility of organics, but doesincrease the volume of the wastes.
Response: Some chemical fixation processes have been shown to be successful at immobilizing certainorganic compounds. Whether a fixation process can be developed to fix the organics presentat this site would need to be determined during a treatability test.
Comment 83: Pave 4-7, 4.1.7 Alternative 7.
It is not cost-effective to construct an onsite landfill for each RMA site. An effort should bemade to relate this interim response action to the Final Remedy, e.g., the prospect that theFinal Remedy may include a landfill and soil treatment process(es) and that, for cost-effectiveness, redundancy should be avoided where possible.
Response: The term "landfill" has been replaced with "temporary waste pile" to clarify the intent of this
storage unit.
Comment 84: Page 4-8, third paragraph.
More important is which organic contaminants are not immobilized by chemical fixation. Thistechnology is highly problematic if some of the organics leach from the matrix. Extensivetesting would be required to determine a recipe for fixation with the possibility that none willwork or be cost effective.
Response: Agreed. This is a consideration of the long-term effectiveness criterion. The potential forsubsequent leaching of organics after treatment is one reason chemical fixation is eliminatedfrom consideration in Section 6.2.
Commcnt 85: Page 4-9, second paragraph.
See Comment No. 83.
Could a landfill be constructed "in the vicinity of the M-1 Settling Basins" without possiblyinterfering with final remedial actions?
Response: The location of the temporary waste pile would be chosen during design and would, to themaximum extent possible, be located to provide minimal interference with the final remedy.
Comment 86: Page 4-12, 4.2 Alternative Evaluation Criteria.
The preeminent criteria is the effectiveness of an alternative in achieving the objective of thisinterim response action, i.e., to mitigate the threat of release of contaminants from the M-1Settling Basins with the goal of providing a benefit to cost or timing of RMA remediation(Section 1.2). This criteria is not addressed in this Section or anywhere else in this assessment.
This Section only defines CERCLA evaluation criteria. An alternative Assessment shouldrelate these criteria to specific site conditions and the specific alternative being evaluated.There should be more focus in this Section 4.0 on this site and on the interim responseobjective and guidelines. The questions listed under the evaluation criteria sections may begenerally applicable to Superfund sites but many of them do not seem applicable to an interimresponse action at this specific site.
Response: The alternative evaluation has been expanded in Section 6.2 of the final alternatives assessmentto discuss these points in greater detail.
(11111CO2.3100) (11/18/89) 21
Woodward-Clyde Conukant
Comment 87: P , second paragraph.
"How each alternative addresses each of the evaluation criteria will be presented ingreater detail in the IRA Decision Document. However, a summary of alternativeevaluation criteria is presented in Tables 4-1a and 4-1b."
Discussion of how the alternatives address evaluation criteria (and most importantly theobjective of the IRA) is the whole point of an Alternatives Assessment document and shouldbe included. The summaries in Tables 4-1a and 4-1b are too brief to be of value. How can theOther Organizations and the State make meaningful comment on the ranking of alternativesin Section 6.0 it there is no such discussion?
Response: All alternatives developed would meet the IRA objective. The alternatives evaluation has beendiscussed in greater detail in Section 6.2 of the final alternatives assessment.
Comment 88: Page..-13, 4.2.1 Effectiveness.
"Some of the questions addressed in this evaluation are as follows:"
None of these questions appear to be addressed in this assessment except in very general termsin Tables 4.1a and -lb. For example, what risks are mitigated by the alternatives described?Section 1.2 states that this site does not appear to pose a significant risk to human or biotareceptors at this time. The site assessment in this evaluation does not demonstrate the M-1Settling Basins are a source of groundwater contamination.
Achievement of the objective of this interim response action should be the preeminent criterionconsidered in this Section.
Response: The objective of this IRA is to mitigate the threat of release from the source. All alternativescarried forward to the expanded evaluation in Section 6.2 meet this objective. Section 2.2.2discusses the evaluation of the ':!-I Settling Basins as a source of groundwater contamination.
Comment 89: Page 4-15, 4.2.2 Reduction in Mobility. Toxicity and Volume.None of the issues listed are discussed with specificity to the respective alternative interim
response action at this site.
Response: See response to Shell's Specific Comment No. 87.
Comment 90: Page 4-16. 4.2.3 Imnlementability.
None of the issues listed are discussed with specificity to the respective alternative response
action at this site.
Response: See response to Shell's Specific Comment No. 87.
Comment 91: Page 4-17, 4.2.4 Overall Protection of Human Health and the Environment.
The presence of a threat from this site to human health or the environment is not discussed.What is the basis for evaluation of alternatives against this criterion at this site?
Response: The Federal Facility Agreement lists the M-1 Settling Basins as a "hot spoCt for which IRAAlternative Assessment is required. The objective of this IRA is to mitigate the threat ofreleases from the M-1 Settling Basins. The M-1 Settling Basins are evaluated as being a sourceof arsenic contamination to the groundwater. The implementation schedule for both the
(11111C02-3100) (11/18/89) 22
Woodwar Cot
Decision Document and the Response Action itself makes it difficult to collect a sufficientamount of data for the comprehensive risk assessment required to determine whether asignificant risk to human health or the environment exists.
Alternatives were evaluated based on their ability to mitigate the threat of releases at the site.
Comment 92: Table 4-1a.
The title of this table states that these are threshold criteria for the Motor Pool Area. Is thetable for another IRA site or is it mislabeled?
Under Overall Protectivcacss, whit sp"I.ifically is "thei risk" against which this criterion isapplied?
Under Comnliance with ARAR's, at this point in the IRA process ARAR's are identified onlypreliminarily. Statements under this column should be qualified accordingly. Also, the abilityof the respective alternative to meet an ARAR mnay not be known prior to testing or design.
Response: The table title has been corrected.
The risk referred to here is any health risk to the community and the environment resultingfrom the presence of arsenic contamination at the site.
For any alternative implemented as an IRA at the M-1 Settling Basins, ARARs would be metto the maximum extent practicable.
Comment 93: Pge 5-, second paragraph.
"Since the Federal Facility Agreement states that the IRA decision document shouldselect the most cost effective alternative which meets the threshold criteria,..."
More accurately, the FFA (Section 22.6) states: "The goal of the asemnt shall be to ...selectthe most cost-effective alternative for attaining the obiective of the IRA" (emphasis added).The objective of the IRA should not be confused with CERCLA evaluation criteria
Response: The text has been changed.
Comment 94: Page...,, third paragraph.
"A present worth analysis is also presented to compare alternatives with differentproject durations."
Since project life is the same (5 yrs) for all alternatives, the present worth analysis is used hereto facilitate comparison of alternatives with different expenditure patterns during the five yearperiod.
Response: The text has been changed to replace "project durations" to "expenditure pattern."
Comment 95: Tables 5-1 to 7.
Why are air monitoring costs in year 0-1 for alternatives involving excavation and/or treatmentthe same as for alternatives 2-5 which do not? Experience of the Basin F IRA implementationshould indicate that air monitoring will be substantially greater for alternatives involvingexcavation and/or treatment.
(11111C02-3100) (11/18/89) 23
Response: Only conceptual alternative designs are presented in the IRA Alternatives Assessment. Themonitoring program outlined is appropriate for this purpose. As with any alternative, changesto the conceptual design may be made during final design.
Comment 96: Table 5-1, (follows nage 5-10).
In general, the costs presented in this table appear to be excessive. For example, the 0 & Mfor labor for air sampling is $80,000, but the air sampling of this site should not. require thislevel of effort. The costs of sampling existing monitoring wells also appears to be inflated.These inflated monitoring costs are carried forward to the estimated costs for the varioustreatment alternatives.
Response: See response to Shell's Specific Commeut Nu. 95.
Comment 97: Table 5-
Why is cap maintenance included in the cost of this alternative? No mention of a cap is madein 4.1.7.
Response: The cap is for the temporary waste pile.
Comment 98: Pae61 6.0 Conclusions.
The preeminent criterion as developed in Section 1.2, i.e., to affect the cost or timing of theFinal Remedy, is not addressed in this classification. (Neither is it addressed under theCERCLA criterion of Effectiveness in Section 4.0). This classification is essentially a rankingby ability to meet CERCLA criteria.
Response: See response to Shell's Specific Comment No. 87.
(11111CO2-3100) (11/11/89) 24
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VI999 18th STREET - SUITE 500
DENVER, COLORADO 80202-2405
Ref: 8HWM-SR
Mr. Donald L. CampbellOffice of the Program ManagerRocky Mountain ArsenalATTN: AMXRM-PMCommerce City, Colorado 80022-2180
Re: Rocky Mountain Arsenal (RMA)Alternative Assessment of InterimResponse Actions (IRA) for OtherContamination Sources: M-iSettling Basins, September 1989.
Dear Mr. Campbell:
We have reviewed the above referenced document and have theenclosed comments. We wish to emphasize our concern that thedocument does not evaluate the potential for continued migrationand treatment of the arsenic plume from the M-i Settling Basins.This possibility should be addressed, given the inability of theboundary or other IRA intercept and treatment systems to treatarsenic.
The document does not adequately assess the M-I SettlingBasins as a source of groundwater contamination nor does itconsider interception and treatment of the groundwater near thesource as a remedial alternative for this IRA. We do not agreewith the limitation of no groundwater remedlation as part of thisIRA, and note that several IRAs are devoted partially orcompletely to the interception and treatment of groundwater.
Our concerns on associated ARARs issues are addressed in aseparate letter. Please contact Linda Grimes at (303) 293-1262,if you have questions on this matter.
Sincerely,
Connally MearsEPA Coordinator for RMA Cleanup
cc: Jeff Edson, CDHDavid Shelton, CDHVicky Peters, CAGOLt. Col. Scott IsaacsonChris Hahn, ShellR. D. Lundahl, ShellJohn Moscato, DOJRobert Foster, DOJ
2
Ii
RESPONSES TO THE EPA-S COMMEN7S ON THE ALTERNATIVES ASSESSMENTOF THE INTERIM RESPONSE ACTIONS FOR OTHER CONTAMINATION SOURCES:
M-1 SETTiNG BASINSNOVEMBE 1989
GENERAL COMMENTS
Comment 1: Page 2-1, Section 2.1.1.2, please expand the text to state the source and nature of the solids,referenced here, which filled the basins.
Response: The solids referenced here consist of a lime sludge generated during the "neutralization' ofwaste streams produced in the lewisite complex, the acetylene plant, the thionylchloride plantand the arsenic trichloride plant in the South Plants area (Ebasco 1987). The waste materialsent to the basins consists predominantly of arsenic salts such as arsenic oxide and arsenictrichloride, mercuric catalyst discarded from the lewisite plant, and lime sludge from theacetylene plant and from the neutralization process.
Comment 2- Page 2-1, Section 2.1.1.2, please state the process used to precipitate the arsenic and thechemical form of the arsenic in the solids.
Response: The waste streams from the lewisite complex were sent to the four disposal reactors at thelewisite disposal facility. There, they were neutralized with calcium hydroxide. Afterneutralization, they were sent to the M-1 Basins to settle. The current chemical form of thearsenic is unknown since analytical meth-'¥ds used during site characterization indicate only"total" arsenic in soil and 'total" and *dissolved" arsenic in groundwater. The chemical state ofthe arsenic could affect the effectiveness of chemical fixation. Treatability testing of thattechnology would be required.
Comment 3: Page 2-5, Section 2.2.2, the first paragraph in this action concludes that the arsenic in thegroundwater is associated with suspended solids. The second paragraph concludes that thearsenic is dissolved in the groundwater. Please explain this apparent discrepancy.
Response: Samples taken in the spring of 1989 were analyzed for filtered and unfiltered arsenic usingstandard USATHAMA methods. The historical data presented in the report did not specifywhich analytical methods were used. Therefore, this discrepancy cannot be positively explained.One possible explanation may be variable sample preparation or preservation methods.
Comment 4: Page 2-13, Section 2.3.3, the statement that the synergism between metals reduces the toxicityis inappropriate in this text and cannot be substantiated for this site. The metals would betaken up by the plants and could be toxic to herbivores.
Response: This section has been significantly modified to address the concerns of the reviewingorganizations.
Comment 5: Page 2-13, Section 2.3.4, the text indicates that metal organic chelates are a nonsoluble metalsform. It is expected that metal organic chelates would be soluble. The text should be amended.
Response: The text has been changed.
Comment 6: Page 2-15, Section 2.5, the text states that dewatering would not be required for this IRA, sincethe alluvial groundwater is 8 feet below the surface. It is possible that groundwater would beencountered during any excavation of contaminated soils in the basins even during seasonallows in water levels. The document needs to address this possibility more directly.
(11111C02-3100) (11/18/89) 25
I Woodward Clye ConsUlants
Response: Possible dewatering and water treatment options are discussed in Section 3.2.7. A decision onwhich method(s) to use, if necessary, will be made during design.
Comment 7: Page 3-2, Section 3.1.2, please expand the text to present the basis for the statement thatgroundwater contaminants appear to be originating from the South Plants Area. Further,please specify which contaminants are being addressed.
Response: Based on groundwater contaminant data reported to the RMA data base and summarized inTable 2-2, there does not appear to be a significant increase in organic contaminants becauseof the M-1 Settling Basins. Also, the soil samples taken from within and in the vicinity of theM-1 Settling Basins do not indicate that the basins are a source of organic contaminants.Therefore, the source of these contaminants is upgradient of the M-1 Settling Basins, and it isassumed that the source is the South Plants area. See Table 2-2 for the contaminants foundin this area. Section 3.1 has been revised to address comments from the Organizations and theState, and this statement has been deleted. The major contaminant apparentl) contributed tothe groundwater by the M-1 Settling Basins is arsenic.
Comment 8: Page 3-2, Section 3.1.2, the text states 'Groundwater remediation is assumed to be beyond thescope of this IRA." This assumption needs to be justified. Considering that the M-1 SettlingBasins are an identified source of arsenic contamination in the groundwater and that none ofthe boundary or other IRA intercept and treatment systems are designed to treat arsenic, thedocument needs to quantify the extent of, and assess the potential remediation of, arseniccontamination in the groundwater. We do not agree with the elimination of groundwaterremediation as an objective of this IRA.
Response: The objective of the IRA is to mitigate the threat of releases from the M-1 Settling Basins.The Army agrees that the contaminated alluvial groundwater emanating from the South Plantswill need to be addressed in the final remedy. However, to attempt to address the groundwatercontamination contributed specifically from the M-1 Settling Basins would require extensiveinvestigation to sort out what contamination was emanating from what source.
Comment 9. Page 3-4, Section 3.2.1, the text states '...apparent relatively immobile compounds present at theNI-1 Settling Basins...'. Please provide further explanation of the meaning of this statement andan assessment of the adequacy of the number of current monitoring wells.
Response: This statement has been removed from the text. Wells 01083 and 36193 were installed duringthe 1989 field program for this task to provide adequate groundwater contaminationinformation. These wells, sampled in conjunction with 01503, 01504, and 01524, are adequateto monitor contaniinant migration from the M-1 Settling Basins.
Comment 10:. Page 3-8, the option to lower the groundwater table by dewatering should be considered. Thiswould enable excavating to occur despite of unfavorable groundwater levels.
Response: Dewatering would be conducted if necessary. Methods of dewatering are discussed in Section3.2.7.1 The presence of groundwater in excavated soil would have little effect on thealternatives develope! for the M-1 Settling Basins and presented in Section 4.0.
Comment 11: Page 3-13, Section 3.2.5.2.2, first paragraph, the fourth sentence states that *...the solution isrecycled until the contaminant concentration in both the soil and treatment solution are equal."The text should be corrected to say "...are in equilibrium.'
Response: The text has been changed.
Comment 12: Page 3-16, Section 3.2.6.1.1, Hazardous Waste Landfill, there is discussion about a hazardouswaste landfill for onsite "disposal" as part of this IRA. It should be noted that the final decisionon this IRA has to be consistent with the final remediation of the overall RMA site. Since it
(1111tC02-3t30) (11/18/89) 26II
is premature to assume that onsite "disposal will be consistent with the final remediation, andsince 22.1 (1) of the FFA specifies "temporary storage', please restate "onsite temporarystorage," and that future remediation may include other actions such as excavation, treatment,and placement.
Response: The text has been changed.
Comment 13: Page 3-21, Section 3.2.7.2.1. Carbon Adsorption, last paragraph of this section makes thestatement that volatile halogenated organics'...are among the least sorbable species withreference to GAC" and that GAC would not be considered further. It should be noted thatthere are several GAC treatment operations on the RMA site which are specifically designedto remove volatile halogenated organics. The text should be amended to clarify what is meantby this statement, and GAC should be retained as a potential water treatment technology.
Response: The groundwater at the M-1 Settling Basins has contaminant concentrations several orders ofmagnitude higher than groundwater being treated by GAC elsewhere at RMA. Excessivecarbon usage rates for these high concentrations makes GAC inappropriate for this site. Thetext has been changed to clarify this point.
Comment 14: Page 3-28, Section 3.2.7.3.1, Reinjection, in this paragraph, injection of water is not consideredfurther because of microbial growth plugging well screens. It should be noted that reinjectionis presently done on the RMA site and appears to be technically feasible; so, it is notappropriate to screen out reinjection in this section.
Response: The use of wells for reinjection was rejected because of potential fouling problems. Reinjectionthrough percolation beds or trenches is considered. The text has been changed to clarify thispoint.
Comment 15: Page 3-28, Section 3.2.7.2.7, Ion Exchange, the last sentence states that both "...anion and cationexchange resins were used in the study, since arsenic may exist in several oxidation states." Itshould be noted that arsenic exists in water as an anionic complex regardless of oxidation state;but most researchers have found that regardless of the removal process for arsenic that it ismost effective to pre-oxidize the arsenic to the +5 oxidation state.
Response: Agreed. The sentence has been deleted.
Comment 16: Page 3-29, please state whether the feasibility of the treatment of groundwater in the proposedCERCLA Wastewater Treatment Plant was evaluated.
Response: The treatment of groundwater in the proposed CERCLA Wastewater Treatment Plant was notevaluated in this IRA Alternatives Assessment because the treatment plant is still indevelopment, and the project has an unknown implementation schedule. Should dewateringand water treatment be necessary, options such as those described in Section 3.2.7 or any newoptions such as the CERCLA Wastewater Treatment Plant would be considered during thedesign and implementation of this IRA.
Comment 17: Table 4-1a, for three alternatives (no action, monitoring, and institutional controls), the tableindicates compliance with ARARs. The table should indicate that there are no ARARs forthese alternatives. In order to determine the acceptability of these alternatives, a risk analysiswould have to be done.
Response: The table has been revised. Monitoring and institutional controls can be designed andimplemented so that location-specific or action-specific ARARs (to the extent they exist) aremet. Since no treatment is involved, ambient or chemical-specific ARARs will not be met.The no action alternative would not trigger location or action-specific ARARs, nor would itmeet ambient or chemical-specific ARARs.
(1111tC02.3100) (11/18/89) 27
Woodward-Cydle Conmutnts
Comment 18. Page 4-3, Section 4.1.2, Monitoring, it is stated that monitoring will be done by quarterlysampling and analyses, and that this information will be included as part of the ComprehensiveMonitoring Program (CMP) as RMA. Please state that the CMP is committed to doing thisoperational monitoring on a quarterly basis.
Response: The monitoring on a quarterly basis will be performed during implementation of this IRA, aspart of this IRA. The statement that this information will be included as part of the CMPimplies that the yearly CMP anaysis of groundwater will include this information.
Comment 19:. Page 3-29, last paragraph, please detail the "discharge limitations' for storm sewer dischargewhich make it appear a more feasible option than discharge to the RMA Sewage TreatmentPlant (STP). Such limitations for a new discharge would have to be developed and would likelyroughly equal those for the STP.
Response: Discharge limitations will be developed during the preliminary design phase of the project.Whether the additional capacity and effluent quality of the selected water treatment unit couldbe introduced into the RMA sanitary sewer is as yet undetermined. Therefore, until theselimitations are set, discharge to the RMA STi cannot be discounted. The text has beenchanged to reflect this fact.
Comment 20-. Page 4-5, first paragraph, please explain the consistency of the 360' slurry wall with the finalremedy.
Response: The purpose of the 360 slurry wall constructed for this alternative is to hydraulically isolatethe M-1 Settling Basins so that groundwater inflow does not interfere with the ISV process.Materials excavated during slurry wall construction would be placed within the slurry wall andvitrified with the other M-I Settling Basins soil/sludge. This would be consistent with the finalremedy because ISV destroys the organics and permanently immobilizes the metals.
(11111C02-3100) (11/18/89) 28
STATE OF COLORADOCOLORADO DEPARTMENT OF HEALTH
4210 East I1th Aven.,eDenver. Colorado 80220Phone (303) 320-8333October 11, 1989R 7ote
Roy~ RomleGOvernt
Mr. Donald Campbell M. W, LDeputy Program Manager I CU DeCw,
Office of the Program ManagerAMXRM-PM, Bldg. 111Commerce City, Colorado 80022-2180
Re: State comments on Draft Final Alternative Assessment of theInterim Response Actions for Other Contaminated Sources - MlSettling Basins.
Dear Mr. Campbell:
The State submits the following comments regarding the DraftFinal Alternative Assessment of the Interim Response Actions forOther Contaminated Sources - M1 Settling Basins.
During the October 5, 1989 Committee meeting, the State wasinformed by a contractor for the Army that numerous additionalsamples had been taken and analyzed prior to issuance of thisreport. According to your contractor,these data, including 30soil samples and 7 ground water samples were omitted from thereport because the report contained sufficient historicalinformation in order for the reader to evaluate thealternatives.
In order for the State to adequately provide comments on thisdocument, we urge the Army to include all available data in thereport. The State had to modify significant portions of theircomments regarding this interim action based on the datapresented during the October meeting.
If you have any questions, please feel free to call.'
Sincere;
f. . dson, Project Manager
SCazardous Materials and Waste Management Division
cc: Michael R. Hope Esq.John Moscato, Esq.Chris HahnEdward J. McGrath, Esq.Connally MearsBruce Ray,Esq.Lt. Col. Scott IsaacsonTony Truschhl
Wooward.Cyd Conadtants
RESPONSES TO THE STATE OF COLORADO'S COMMENTS ON ALTERNATIVEASSESSMENT OF iNTERIM RESPONSE ACTIONS FOR OTHF.=
CONTAMINATION SOURCES M-1 SETrUNG BASINSNOVEMBER 18
GENERAL COMMENTS
Comment 1: In the M-1 Settling Basins IRA Alternative Assessment, the Army contemplates a myriad ofresponse actions that apparently provide for ultimate remediation of this particular source.Such activities are beyond the scope of the "other sources IRA" as discussed in 1987 when theState concurred in the designation of this IRA. The original objective envisioned by the Statewas to expeditiously contain or remove source material and thereby halt further migration ofhighly concentrated waste into ground water or soils. The alternatives presented by this reportinclude several relatively innovative technologies which are currently in various experimentalstages but remain basically unproven. Although this document seems to indicate that theycould be implemented within a year, this seems unlikely given the detailed field proofing andpi!3t testing that would be necessary to ensure proper performance. Inclusion of these timeconsuming efforts in the interim action process will unduly delay implementation. In addition,adoption of such treatment alternatives on a source by source basis may prove to beinconsistent with the final remedy selected at the Arsenal, or result in costly duplicative efforts.
The most obvious and appropriate interim response alternative, excavation and temporarystorage in a sufficiently protective waste pile, was not even considered. The report shouldtherefore be revised to include this alternative. The report should also include any proventreatment technologies that could be implemented on an expedited basis and would bereasonably certain to achieve agreed upon cleanup criteria, if such technologies currently exist.
Response: The Army disagrees with the State of Colorado's opinion that treatment alternatives arespecifically excluded from the scope of the "other sources IRA." Paragraph 22.6 of the FederalFacility Agreement states that "The goal of the assessment shall be to evaluate appropriatealternatives and to select the most cost-effective alternative for attaining the objective of theIRA." The objective of the IRA is "To mitigate the threat of releases from the M-1 SettlingBasins." The Army has evaluated a broad range of alternatives including, but not limited to,containment, treatment and temporary storage. The Army has evaluated these alternativesbased on criteria recommended in the CERCLA Guidance with emphasis on implementabilityand consistency with a final response action. Therefore, technically immature treatmentalternatives or alternatives with excessive implementation periods would be discounted in theevaluation process. If a treatment alternative is selected, it would necessarily be one whichcould be implemented with minimal field testing and be completed in a time frame consistentwith the overall IRA implementation schedule.
Excavation and temporary storage was considered and discounted early in the selection process.The sludge currently exists sub-grade with no significant impacts to the community or biota.The only significant impact is on alluvial groundwater quality. The excavation operation couldpotentially release possible lewisite or Army agent degradation products present in the sludge.Any precipitation runoff or leachate collected from the temporary storage pile would requiresubsequent treatment. The Army sees no benefit in the excavation of this material only to storeit, untreated, onsite. There are less expensive containment alternatives (slurry wall and cap),and treatment options that are better suited to this particular site.
Comment 2- Data presented at the October 5, 1989 RMA Committee Meeting indicated that the Army hasconcluded that lhe M-1 basins are a major source of groundwater contamination, particularlyarsenic. The horrendous concentrations detected in the vicinity of these ponds are particularlydisturbing given the fact that they will not be treated either at the Basin A Neck treatment
(11111C02-3100) (11/18/89) 29
5 Woowar Clyde Consulants
facility or at the boundary systems, none of which, despite repeated State protestations, treatU. inorganics. The State again strongly urges the Army to address inorganic contamination at theArsenal on an expedited basis.
Response: The Army fully intends to address inorganic contamination at the arsenal during considerationof final remediation at RMA. The objective of this IRA is to mitigate the threat of releasesfrom the M-1 Settling Basins. The Army's interpretation of this objective is that thecontamination source will be addressed in an expeditious manner. To include groundwatertreatment in this IRA runs the risk of slowing the implementation schedule.
Comment 3: The descriptions of the evaluated technologies do not indicate the degree of cleanup that wouldbe achieved by their implementation. The ARARs analysis offers neither ARARs nor proposedremedial objectives for these technologies. Without knowing the degree to which eachalternative will succeed in removing or immobilizing contaminants, the parties cannot applythe ARARs and protectiveness evaluation criteria to determine the most appropriate responseaction.
Response: Action-specific ARARs, and location- and chemical-specific ARARs should be met to the* maximum extent practicable.
Comment 4: At the October 5, 1989 RMA Committee Meeting, Army contractors presented additional fielddata regarding the M-1 Basins, among other sources. Although this sampling had beenperformed some months previously, the data were not incorporated into the AlternativesAssessment document. The absence of these data hampered the State's ability to thoroughlyreview and analyze the Assessment. All data obtained on these basins, and conclusions drawnfrom these data should be included in this report and subject to review by the parties.
Response: In order to meet the schedule, it was necessary to issue the Alternative Assessment of InterimResponse Actions for other contamination sources, M-1 Settling Basins, to the Organizationsand the State for comment prior to the validation and distribution of the laboratory data fromsamples collected during the field investigation for this Task Order. Data from the 1989 fieldinvestigation are presented in detail in the Field and Laboratory Investigation Report for this
investigation (WCC 1989). This alternatives assessment summarizes the data, with data fromprevious investigations, in Tables 2-1 and 2-2. These data confirm that the M-1 Settling Basinsare a source of groundwater contamination. This conclusion is also discussed in the Field andLaboratory Investigation Report.
Comment 5: The State noted several inconsistencies and contradictions between data presented in the DraftAssessment and the Task 24 Final Phase I Army Spill Sites Data Presentation Report for theSouth Plants Manufacturing Complex (9/89), as well as the South Plants Study Area Report(SPSAR, 6/89). These inconsistencies and contradictions are further discussed in the specificcomments below. These problems should be acknowledged in this report and resolved as soonas possible, if necessary with additional field studies.
Response: Any inconsistencies will be addressed under the specific comments.
SPECIFIC COMMENTS
Comment 1; -Pag1-&1 - The candidate selection criteria discussed on pages 1-3 & 1-4 do not accordwith the flow chart presented as Figure 1-2. Specifically, the flow chart's initial diamond whichpres ,s the threshold question of whether the site is an active, primary source ofconta-nination does not limit that question to an assessment of the site's effect on ground water.Such a limitation was expressly disapproved by State representatives at the June 7, 1989subcommittee meeting which was held to discuss screening criteria for the 'other sources" IRA.
(1111IC02-3100) (11/18/89) 30
I
Woodwa Clyde
Secondly, the first bullet under the third criteria, which is suppose to accord with the thirddiamond on the chart should be changed to address the question of accelerated clean-up. Thequestion currently posed: 'Will interim action reduce risks?" is vague and undefined andshould more appropriately be applied as an evaluation criteria by which to judge proposedremedial alternatives.
Response: The fact that the M-1 Settling Basins contain a lime sludge contaminated with highconcentrations of arsenic is well known from historical data and previous studie-. The basinshave been covered since about 1947 with soil and/or structures (concrete pads and tanks). TheArmy did not limit its analysis to the site's effect on groundwater; however, since thecontaminated sludge is below grade and has been covered with soil/structures for approximately40 years, air emissions from the sludge are considered unlikely. The dirt road across the siteand structures presents limited contact with burrowing animals and the site is not vegetated soimpacts on biota are not considered significant. The Army's major concern and the emphasisof this assessment is the threat of release of arsenic contamination to the groundwater fromthe M-1 Settling Basins.
Secondly, the Army agrees that adding a statement on accelerated cleanup would clarify thediscussion on page 1-4 and the text has been changed. The major risk at this site is the threatof release of contamination from the M-1 Settling Basins to the groundwater. Acceleratedcleanup would reduce that risk.
Comment 2- PageI - The benefit in performing an interim action to remediate a source under the "OtherSources" IRA should be analyzed in the Alternative Assessment Document, not in the DecisionDocument as proposed by the Army. Unless such a benefit is recognized, the Army shouldnot be expending time and resources evaluating alternatives.
Response: Agreed. The benefit in performing an IRA is discussed in the expanded evaluation presentedin Section 6.0.
Comment 3: Page 3- - The introductory paragraph indicates that an interim action objective is to treat "thesoil and groundwater to protect human health and the environment" (emphasis added). Inother portions of the report the Army has stated that this IRA will not address groundwaterremediation. These contradictory statements must be reconciled.
Response: The text of this paragraph has been changed. Groundwater treatment in the vicinity of the M-1 Settling Basins is beyond the scope of this IRA.
Comment 4: P - It is not clear why the Army has limited offsite alternatives to chemicalfixation/stabilization. This choice must be explained and justified.
Response: Because the M-1 Settling Basins were used to treat waste fluids from the lewisite disposalfacility, there is some possibility that some lewisite or breakdown products may exist in thebasins. This possibility precludes the feasibility of taking untreated M-1 Settling Basins sludgesoffsite for treatment.
Comment 5: P - In section 3.2.5.4.1, the Army states that off-site chemical fixation/stabilization"utilizes readily available materials and equipment, is technically feasible, and will be consideredfurther"; however, it is not evaluated in chapters 4 and 5, nor is it ranked in chapter 6. Thereport should be revised, therefore, to include a detailed evaluation of this alternative.
Response: The text has been changed to state that this is technically feasible. It will not necessarily beconsidered further. This technology was not included in an alternative because of thepreference to treat on site, as discussed in Section 1.1.
(11111C02-3100) (11/18/89) 31
SWoodward-yf do
Comme n 6: P - A hazardous waste landfill must also meet the requirements of 6 CCR 1007-3 section 264 subpart N and 6 CCR 1007-2. Even a cursory review of State siting requirementsindicates that a hazardous waste landfill could not be located in the vicinity of the M-1 ponds;therefore, this alternative should be eliminated from further consideration.
In addition, the construction of a landfill is not appropriately conducted under a. IRA and maybe inconsistent with the final remedy selected for the entire Arsenal. Any residual wastes musteither be disposed of off site or temporarily stored in a waste pile.
Response: The onsite landfill discussed in this Alternatives Assessment is intended to be used fortemporary storage until re-evaluation during final remediation. The text has been changed toclarify this point. The term "onsite landfill* has been replaced with 'temporary waste pile.* Thelocation of the temporary waste pile would be chosen during implementation. The waste pilewould be constructed to meet ARARs to the maximum extent practicable.
Comment 7: Pge.3-1 - The Army would also need to comply with State regulations regarding thelandfiling of solid waste. See 6 CCR 1007-2.
Response: Acknowledged. Construction of an onsite temporary wastepile would comply with ARARs tothe maximum extent practicable.
Comment 8: Page 3-1 - If the shallow aquifer is in contact with contaminated material within the basins,as it appears to be, dewatering will be necessary to ensure complete excavation and propertreatment of the basin materials. Unless all of the contaminated materials are effectivelyremoved from the basins or treated, they will continue to contaminate the underlying groundwater.
Response: Agreed. Decisions on dewatering and water treatment methods, if necessary, would be madeduring design. A distinct advantage to in situ vitrification is that any water encountered duringoperation would essentially be "boiled off' and condensed in the offgas collection and treatmentsystem. Any associated organic contaminants would be pyrolyzed in the melt.
Comment 9. 3 - In section 3.2.7.3.1, the Army rejects as a treated water disposal alternative, thereinjection of extracted water into aquifers underneath the Arsenal, yet this method has beenchosen not only at the boundary systems, but also for other IRAs such as the north of BasinF intercept and the Basin A Neck intercept systems. This report should explain why a
technology chosen for these other response actions is inappropriate under the circumstances of3 this IRA.
Response: The Army screens out the use of wells for reinjection because of potential fouling problems.Reinjection through percolation beds or trenches is considered. The text has been revised toclarify this point. Decisions on dewatering and water treatment methods, if necessary, wouldbe made during design.
Comment 10. Pae3- - In section 3.27-3.3, the Army points out the problems that would be created bydisposing of treated water into the sanitary sewers. The State has previously raised theseconcerns in relation to Army proposals to discharge CERCLA wastewater, hydrazinewastewater and 1727 liquids into this system; however, these concerns have been ignored. Whyare the problems identified in this section not of concern for the other IRAs?
The report should also evaluate the possibility of routing the dewatered fluids to the CERCLAwastewater treatment facility.
1 (11111C02-3100) (11/18/89) 32
I Woodward-Clyde ConmtantsIResponse: The State is incorrect in saying that the Army has proposed the direct discharge of any RMA
wastewaters into the sanitary sewer. The discharge of wastewater oly after treatmen to levelsspecified by ARARs has been proposed for other IRAs, i.e. CERCLA Liquid Waste, HydrazineFacility, and Building 1727 Sump. The intent of Section 3.2.7.3.3 was not to point out problems,which the Army does not foresee, but to point out the minimal requirements of treatment priorto discharge into the sanitary sewer. Concerns regarding the CERCLA wastewaier treatmentfacility, the Hydrazine IRA, and the 1727 Sump IRA have been addressed in the documentationfor those actions and in revisions to the NPDES permit. The State's assertion that, "theseconcerns have been ignored" is incorrect. A significant distinction in considering treatment ofwastewater from this IRA is the potential high arsenic concentration.
Use of the proposed CERCLA wastewater treatment plant for groundwater treatment was notevaluated in this IRA Alternatives Assessment because the treatment plant is still indevelopment. Should dewatering and water treatment be necessary, options such as thosedescribed in Section 3.2.7 or any new options such as the CERCLA Wastewater Treatment
i Plant would be considered during the design and implementation of this IRA.
Comment 11: Page3-20 - The discussions of water treatment processes contained in Section 3.2.7.2 do notinclude projections of the water quality to be achieved by each technology;, nor does the DraftARARs document set ARARs or remedial action objectives for the organics that have beendetected in the ground water underlying the basins. Without knowing the effectiveness of eachtreatment process, the parties cannot assess the alternatives in accordance with the ARARs and3 protectiveness evaluation criteria.
Response: It is not the intent of this alternatives assessment to set effluent water quality standards orobjectives. Water treatment technologies were screened based on their ability to treat highconcentrations of organics in water. If any water treatment is necessary, the process(es) wouldbe designed to meet all ARARs identified.
Comment 12- The description of alternative 7 does not indicate whether chemical fixation will result in amaterial which would be classified as a hazardous waste; thus, it is not clear whether the landfilldescribed would be a solid waste or hazardous waste unit. As noted in specific comment 6
above, a hazardous waste landfill at RMA, especially in the vicinity of the M-1 Settling Basins,would not meet the State's siting requirements for hazardous waste disposal facilities.
Response: The onsite landfill discussed in this alternatives assessment is meant to be for temporarystorage of the treated materials until the final remedy. The text has been changed to clarifythis by replacing the term "landfill" with "temporary waste pile." The location of the waste pilewould be chosen during implementation. The waste pile would be constructed according toARARs, to the maximum extent practicable.
Comment 12 Table 4-1a - This table indicates that an onsite wastepile would not comply with requirementsfor detection monitoring but does not explain why the Army would not perform suchmonitoring. Any on-site landfill must comply with the appropriate State and federal3 requirements regarding groundwater monitoring.
Response: See response to the State's first Specific Comment No. 12. It was assumed, for the purposesof this alternatives assessment, that groundwater monitoring would be performed using existingmonitoring wells rather than constructing new wells because the waste pile is for temporarystorage. The need for additional monitoring wells will be assessed during implementation.
Comment 13: Pag 6- - Offsite disposal is not significantly more expensive than in-situ vitrification andshould therefore be considered a preferred alternative. Potential liability is not an evaluation
S(11111C02.3100) (11/13/89) 33
I
CWoodw-lyde Co
criteria recognized by CERCLA, the NCP, the Federal Facility Agreement or the Task Plan forthe Remediation of Other Sources IRA which was finalized this past Spring. Besides, shouldGrassy Mountain ever become subject to CERCLA remedial action, the Army is already apotentially responsible party for that cleanup since they previously arranged for the disposalof 78,000 barrels of RMA hazardous wastes at that facility in 1986. The potential and extentof liability can be minimized by complying fully with all federal and State regulations regardingthe transportation and disposal of hazardous wastes.
Response: Cost was not the only criteria used to evaluate whether an alternative is preferred, marginallypreferred, or not preferred. As stated on page 6-1 of the Draft Final Assessment, 'Marginallypreferred alternatives meet the threshold criteria listed in Table 4-1a to some degree and meetsome of the evaluation criteria listed in Table 4-lb." The criteria of 4-1b, in addition to cost,include implementability, long-term effectiveness, short-term effectiveness, and reduction ofmobility, toxicity, and volume. There is also an express CERCLA preference for onsitetreatment. The Army agrees that potential liability is not an evaluation criteria; it is only anaspect of long-term effectiveness. The state should note that all preferred and marginallypreferred alternatives are considered further in the decision process. Offsite disposal istherefore considered further.
Commcnt 14: Many of the treatment technologies described in this alternative assessment cannot beadequately evaluated without site-specific treatability studies. This is particularly true for thein-situ treatment technologies, the ability of which to achieve the protectiveness criteriadescribed in Section 4.2 can only be ascertained with bench or pilot testing. These activities areinvariably time consuming, yet they are necessary for an accurate assessment of feasibility andeffectiveness. The report does not acknowledge these realities; therefore, it must be modifiedto include these considerations when assessing "implementability" and scheduling.
Response: Bench scale testing of both ISV and chemical fixation has already been performed. Results ofthese tests are presented in the Field and Laboratory report (WCC 1989). In order to proceedwith the ISV, about six additional borings would need to be drilled and soil samples taken toevaluate a more exact depth of contamination. This could be done during the design phase ofthe IRA. No additional pilot testing is required. For chemical fixation, additional sludge/soilsamples would be sent to vendors during the bidding process. This could also be done duringthe design phase of the IRA.
Comment 15: As discussed in general comment number 5, the State has noted several difficulties with thesource characterization data presented in this report, and in those reports referenced incomment 5. These difficulties include the following:
A) As-built drawings of the three unlined basins on site indicate that basin dimensionsare 115 x 90 x 7 ftW (Alternative Assessment Document, page 2-1). Assuming a totalsurface area of 115 x 300 ft', or 34,500 ft2 (Table 2-4), this results in a total sludgevolume of 9,000 yd3 The site was regraded in 1947, and covered with 2-to-4 feet ofimported soil (page 2-2), which translates to a basin-bottom depth of 9-to-ll feet belowland surface. However, in a volume calculation presented on page 2-15 and in Table2-4, the Army assumed that "waste material extended to a depth of seven feet belowground surface". Subtracting an assumed two foot thickness of imported soils resultedin a total sludge volume of 6,400 yd3 . This calculation, therefore, is not based on theseven foot thickness of the basins as indicated in the as-built drawings, but anerroneous &iZ foot thickness. The basin dimensions of 115 x 90 x 7 ft also differ fromthe 100 x 75 x 5 fti basin dimensions presented in the Army Spill Sites Report (page8).
(1111tC02-3100) (11/18/89) 34
WPodwardC-yd
B) The Alternative Assessment Document (page 2-4) states that six soil borings were
completed in and around the perimeter of the M-1 Settling basins. However, thereferenced figure (Figure 2-1) actually shows eight soil borings and there is no cross-referencing between the text and figure to clarify this discrepancy. The number systemfor the eight borings is also not consistent with the borings presented in the Army SpillSites Report I (Plate 24S-1). Only three borings were completed in this study, twoadditional borings were not analyzed due to the presence of lewisite. Because basinperimeters are not marked on Plate 24S-1, it is difficult to determine coring locationswith respect to the pits. However, it appears that only one boring (Boring 4) may haveactually been completed within a basin. Nowhere in the text is there an indication thatthe bottom of any of the three basins was encountered.
The SPSAR states that only one of three borings in the Task 24 Army Spills programwas completed. This contradicts the data presented in the Spill Sites Report. TheSPSAR also states that additional borings completed by the Army and Shell (noreference given) were only completed to five feet below land surface, and did not reachthe bottom of the basins. The soil boring locations presented in Figure SPSA 1.4-2 do
not match either those presented on Plate 24S-1 of the Spill Sites Report, or Figure2-1 of the Alternative Assessment Document.
c) In addition to the above discrepancies, data presented in the M-1 BasinsAlternative Assessment Document are ambiguous. Table 2-1 presents a summary ofcontaminants in soils and sludge, but does not correlate soil boring number/locationand sample depth with contaminant concentration, or indicate from which of the two
references (D.P. Associates, Inc., 1989a; Ebasco Services, Inc., 1988) the data werecited. Because of the inconsistencies between the three reports with respect to boringlocations/numbers, it is impossible to validate or invalidate Table 2-1 entries.
D) In the groundwater contamination summary presented in Table 2.2, wellnumbers/locations are not correlated to sampling episode, contaminant concentration,or a cited source (D.P Associates, Inc., 1986; D.P. Associates Inc. 1989b). The dataappear to be from alluvial wells 01503, 01504, 01077, 01083, 01524, 36001, and 36193as shown in Figure 1-1, but this is not stated in the text or table. The Army mustfurnish actual well numbers referenced in the table.
If these seven wells do comprise all wells from which the data were compiled in Table2-2, then data gaps exist. Wells 01503 and 01504 appear to have been sampled forvolatiles, semi-volatiles, and pesticides prior to 1984 only, current data are notavailable. New wells 36193 and 01083 are not being monitored in the ComprehensiveMonitoring Program (CMP), and therefore data for the above analyte groups are alsonot available for these wells. Well 01077 is not listed in the RMA GroundwaterChemical Data Base as of 12/88.
Response: (A) The as-built drawings show the three M-1 Settling Basins each to be 115 feet by90 feet by 7 feet deep. The 7-foot depth consists of 5 feet of sludge in the bottom ofthe basins, and 2 feet of soil overburden. Soil borings taken during the 1989 fieldinvestigation confirmed the depth of the sludge (WCC 1989). We noticed thediscrepancy with the Army Spill Sites Report, and chose to use the as-built drawingsfor the evaluation basis.
(B) Figure 2-1 has been corrected to show the six soil borings drilled during previousinvestigations. Three were drilled during the Army Spill Sites investigation. The otherthree were drilled in 1986 and the data are in the RMA data base. The data fromthese borings are summarized in Table 2-1.
(11111C02.3100) (11/18/89) 35
Discrepancies between the South Plants SAR and the Army Spill Sites Report were notaddressed. Data from the Army Spill Sites Report were used in this AlternativesAssessment. The discrepancies do not affect the conclusions or recommendations ofthis alternatives assessment.
(C) Table 2-1 is intended to summarize the contaminants found in the M-1 SettlingBasins sludge, and the soil surrounding above, and beneath the sludge. Data from thetwo references cited were used, as well as data from the 1989 field invest.gation kWCC1989). Please see the RMA data base, the Ebasco report, and the WCC report foradditional details.
(D) The upgradient and downgradient well numbers have been added to Table 2-1.The table is intended to present a summary of contaminants found in the groundwater;not a detailed analysis.
The data from these seven wells are enough to show that the M-1 Settling Basins area source of groundwater contamination. These wells would also be sufficient for futuremonitoring activities to provide information on groundwater contamination trendsinfluenced by the M-1 Settling Basins.
Comment 16: Additional characterization of the source is needed before an appropriate alternative can beselected and implemented. Site characterization should consist of data collection designed todetermine:
A) more precise dimensions of the M-1 Settling Basins;
B) thickness of overlying soils;
C) lateral and vertical extent of soils and sludge contamination; and
D) interaction of alluvial groundwater with basin contaminants.
Response: The Army believes sufficient data is available to support an assessment of alternatives. TheArmy disagrees with the State's assumption that significant additional characterization isrequired at the site. Additional characterization is inconsistent with the spirit of an InterimResponse Action, which is intended to respond to a contamination source in an expeditiousmanner. Some additional site characterization may be necessary for some alternatives duringthe design phase of the IRA, specifically to identify more exact lateral and vertical extent ofsoils and sludge contamination.
(11111C02-3100) (11/18/89) 36
1 S/12/SS 1131? 3I 9 364931 S ?7764 31 USFWS CSO 61
-. United States Department of the InteriorFISH AND WILDLIFE SERVICE
COLORADO FIELD OFFICE?M SIMMS STREET
ROOM 291GOLDEN. COLOR.ADO a0m0
SINr RELY LEVlEt T,0
FWE/CO
Mr. Donald L, CampbellOffice of Program ManagerBuilding IIIRocky Mountain ArsenalCcmmerce City, CO 80022
V'lr Mr. Campbell:
ýe have reviewed the following documents and have no comnients on them at th~s"r .e: (1) Rocky Mountain Arsenal Offpost Private Well Inventory and •
f'r)r-ation Survey; (2) the Draft Final Assessment Reports for the M-I Basins;•ction one and the Motor Pool area in Section 4 of the Rocky MountL .
- ýial; (3) and, the Applicable, Relevant and Appropriate Regulations.,':AR's) pertaining to these sites .
We appreciate the opportunity to review and comment on the documents.
Sincerely,
LeRoy W. CarlsonColorado State Supervisor
cc: Pete Gober, FWSTom Jackson, FWSBob Stewart, DOIDavid Anderson, DOJ'Connally Mears. EPA
